What is the main purpose of the exhaust system?

The exhaust system is a system of pipes and components whose task is to remove and purify exhaust gases, reduce noise and support engine operation.

What does exhaust gas purification system mean?

It is a set of components, such as a catalytic converter, DPF filter and EGR valve, whose task is to reduce harmful chemical compounds in exhaust gases and meet emission standards.

What is a lambda probe used for?

The lambda sensor monitors the composition of the fuel-air mixture and sends data to the engine control unit, which allows for optimal combustion.

How to recognize catalytic converter damage?

Symptoms include a loss of engine power, a check engine light and a characteristic exhaust smell.

Does a DPF filter fit every diesel?

No, DPF filters vary in design and parameters. They must be matched to the make, model, and emissions standard (e.g., Euro 5, Euro 6).

How often should a muffler be replaced?

Under normal operating conditions, an exhaust muffler can last up to 80,000–120,000 km, but its durability depends on the quality of the materials and driving style.

Are the exhaust system parts used safe?

Yes, provided they are verified and come from a reliable source – just like in the Global Parts store, where each part undergoes quality control.

Exhaust systems and exhaust gas treatment

At Global Parts, we offer a wide selection of original used car parts, including exhaust systems and exhaust aftertreatment components for many popular car brands such as BMW, Mini, Mercedes, Audi, Volkswagen, and others. Each part we offer undergoes quality control to ensure you receive a top-quality product.

More information

Make

Category

Subcategory

Condition

In Stock

Price

Products in promotion

Part no. 04E906262AR

Audi A3 8V 30 TFSI Petrol Oxygen Lambda Sensor 04E906262AR

Product currently unavailable

Part no. 8K0131205D

Audi A4 B8 3.0 TDI Quattro Vacuum Connection Pipe Hose Line 8K0131205D

Product currently unavailable

Part no. 05L131765Q

Audi Q5 FY A7 4G 3.0 TDI Diesel DPF Catalytic Converter 05L131765Q

Product currently unavailable

Part no. 04L131512BQ

Audi A3 8V 30 TDI DGTE Exhaust EGR Cooler 04L131512BQ

Product currently unavailable

Part no. 070906252B

Exhaust Lambda Audi A4 B6 B7 A8 D3 Diesel Engine Oxygen Sensor 070906252B

Product currently unavailable

Part no. 04E906262BA

Audi A1 8X VW Polo 6R 1.4 TSI Petrol Lambda Oxygen Sensor 04E906262BA

Product currently unavailable

Part no. 079959231B

Audi S5 8T 4.2 FSI CAUA Petrol Secondary Emissions Smog Air Pump 079959231B

Product currently unavailable

Part no. 8U0253825B

Audi Q3 8U Exhaust Muffer Pipe Tube Tips Set 8U0253825B

Product currently unavailable

Part no. 59001091162

Audi A6 C6 3.0 TDI Turbocharger Exhaust Manifold Elbow Connector 59001091162

Product currently unavailable

Part no. 057131501G

Audi Q7 4L 4.2 TDI BTR Exhaust Gas Recirculation EGR Valve 057131501G

Product currently unavailable

Part no. 06E906265AB

Audi A6 C7 A7 4G Exhaust Lambda Probe Oxygen Sensor 2.8 TFSI CHVA 06E906265AB

Product currently unavailable

Part no. 059906262E

Audi A4 B7 Diesel Line Lambda Probe Oxygen Sensor 059906262E

Product currently unavailable

Part no. 1K0253141D

VW Touareg 7L Audi A3 8P A4 B8 Q7 4L Exhaust Clamp Holder Support 1K0253141D

Product currently unavailable

Part no. 06H906283E

Audi S1 8X S3 8V VW Golf Mk7 2.0 TFSI Vacuum Line Solenoid Valve 06H906283B

Product currently unavailable

Part no. 03L131512C

Audi A3 S3 8P EGR Valve Engine Exhaust Cooler 03L131512C

Product currently unavailable

Part no. 059906629A

Solenoid Valve Audi A6 C6 Q7 4L TDI Diesel Vacuum Pressure Valve 059906629A

Product currently unavailable

Part no. 1K0253141H

Audi A6 C6 A8 D3 Exhaust Clamp Pipe Bracket Mounting Holder 60mm 1K0253141H

Product currently unavailable

Part no. 06F906262AJ

Audi A3 8P 1.6 Petrol Lambda Oxygen Exhaust Sensor Cable 06F906262H 06F906262AJ

Product currently unavailable

Part no. 4G0253350H

Audi A6 C7 A7 4G8 3.0 TDI Front Exhaust Pipe Downpipe 4G0253350H

Product currently unavailable

Part no. 06H906283J

Audi S3 8V VW Golf Mk7 2.0 TFSI Vacuum Line Solenoid Valve 06H906283J

Product currently unavailable

Part no. RS3-8P-EXHAUST

Audi RS3 8P Milltek Sport Rear Exhaust System Muffler Back Box 2.5 TFSI

Product currently unavailable

Part no. 07C906262BH

Audi A3 8P 1.4 TSI Lambda Sensor Oxygen Sensor Lambda Probe 07C906262BH

Product currently unavailable

Part no. 059253034AC

Audi A5 8T 3.0 TDI CCWA Diesel Exhaust Manifold 059253034AC

Product currently unavailable

Part no. 8V3253609M-1

Audi S3 8V Quattro 2.0 TSI DJHA Rear Muffler Active Exhaust Valved Resonator

Product currently unavailable

Audi A5 F5 2.0 TDI DEZE Diesel Engine Exhaust System Clamp 70mm 8W0253141

-5%

Part no. 8W0253141

Audi A5 F5 2.0 TDI DEZE Diesel Engine Exhaust System Clamp 70mm 8W0253141

Product currently unavailable

Part no. 8W0907807G

Audi A4 B9 Exhaust Temperature NOX Sensor 3.0 TDI Diesel 8W0907807G

Product currently unavailable

Part no. 8K0906262

Audi A4 B8 1.8 TFSI Exhaust Lambda Oxygen Sensor Probe 8K0906262

Product currently unavailable

Part no. 059129712

Audi Q7 4L 3.0 TDI Diesel Intake Manifold Inlet Pipe Tube Right O/S 059129712

Product currently unavailable

Part no. 059253033AQ

Audi A5 8T A6 C7 3.0 TDi Diesel Exhaust Manifold Left Side N/S 059253033AQ

Product currently unavailable

Part no. 8E0254302

Audi A4 B7 Exhaust Pipe Tube 8E0254302

Product currently unavailable

Part no. 8Y0253825B

Audi S3 8Y Quattro Rear Muffler Exhaust Ends SET Chrome 8Y0253825B

Product currently unavailable

Part no. 5Q0131971B

Audi A3 8P AdBlue Pump Exhaust Emission Additive Ad Blue Tank Pump 5Q0131971B

Product currently unavailable

Part no. 070131548C

EGR Cooler Clamp Volkswagen Skoda SEAT Audi Pipe Connector 070131548C

Product currently unavailable

Part no. 8Y0253826

Audi S3 8Y Quattro Rear Muffler Exhaust Ends SET Chrome 8Y0253826

Product currently unavailable

Part no. 079253034AK

Audi S5 8T Quattro Petrol 4.2 FSI V8 Exhaust Manifold Cyl. 1-4 079253034AK

Product currently unavailable

Part no. 8K0906088A

EGT Sensor Audi A7 4G8 A6 C7 3.0 TDI CDUC Exhaust Temperature Sensor 8K0906088A

Product currently unavailable

Part no. 3G0131553B

Audi S3 8Y Exhaust Control Line Temperature Sensor Hose Pipe 3G0131553B

Product currently unavailable

Part no. 8W0253825E

Audi A4 B9 Rear Bumper Exhaust Pipe Tip Rear Left Right N/O/S 8W0253825E

Product currently unavailable

Part no. 07L906262G

Oxygen Sensor Audi A6 S6 C6 Exhaust Lambda Probe Unit 07L906262G

Product currently unavailable

Part no. 07Z906051B

Audi A4 B8 A5 8T Q5 8R Q7 4L Gas Exhaust Pressure Sensor Control 07Z906051B

Product currently unavailable

Part no. 06A253033AJ

Audi TT Mk1 8N 1.8T BAM Petrol Engine Exhaust Manifold 03G129969AC

Product currently unavailable

Part no. 04E906262DB

Audi A1 8X 1.0 TSI VW Polo 6R Petrol Exhaust Lambda Oxygen Sensor 04E906262DB

Product currently unavailable

Part no. 03C253041BH

Audi A1 8X Exhaust Manifold Engine Heat Shield Protection Plate 03C253041BH

Product currently unavailable

Part no. 06A919529

Audi TT 8N 1.8T Exhaust Gas Temperature Sensor 06A919529

Product currently unavailable

Part no. 06N145710B

Audi S3 8Y Turbo Boost Pressure Control Valve Unit Sensor 06N145710B

Product currently unavailable

Part no. 8E0906615B

Air Pump Bracket Audi A4 S4 B7 Secondary Mount Holder 8E0906615B

Product currently unavailable

Part no. 059131055M

Audi A6 C7 3.0 TDI High Pressure Vaccum Hose EGR Valve Line 059131055M

Product currently unavailable

Part no. 057131534R

Audi Q7 4L A8 D4 EGR Connecting Pipe Hose Line Tube Right O/S 4.2 TDI

Product currently unavailable

Part no. 059131525BN

Audi Q7 4L 3.0 TDI CRCA Diesel EGR Valve Line Hose Pipe Tube 059131525BN

Product currently unavailable

Part no. 03C253041BB

Audi A3 8P 1.4 TFSI CAXC Petrol Turbo Heat Shield Exhaust Manifold 03C253041BB

Product currently unavailable

Part no. 8S0253826A

Audi TT 8S Rear Exhaust Tail Pipe Tip Left Right N/O/S SET 8S0253826A 8S0253825A

Product currently unavailable

Part no. 057253033BJ

Audi A8 D4 Exhaust Manifold Left N/S 4.2TDI Diesel Engine 057253033BJ

Product currently unavailable

Part no. 057253034BJ

Audi A8 D4 Exhaust Manifold Right O/S 4.2TDI Diesel Engine 057253034BJ

Product currently unavailable

Part no. 06E253032K

Exhaust Manifold Audi A4 B8 A5 8T 3.2 FSI V6 Cyl. 1-3 Right O/S 06E253034F

Product currently unavailable

Part no. 06A253031CK

Audi A3 8P Exhaust Manifold 1.6 MPI BSE 06A253031CK

Product currently unavailable

Part no. 06E253031K

Exhaust Manifold Audi A4 B8 A5 8T 3.0 FSI V6 CALA Cyl 4-6 Left N/S 06E253033F

Product currently unavailable

Part no. 04L131512D

Audi A3 8V Q3 8R EGR Valve Cooler 2.0 TDI 04L131512D

Product currently unavailable

Part no. 07L906262F

Audi A8 D3 Exhaust Gas Temperature Lambda Probe Oxygen Sensor 07L906262F

Product currently unavailable

Part no. 059906627N

Audi SQ5 8R Exhaust Boost Pressure Solenoid Valve 059906627N

Product currently unavailable

Part no. 07L906262B

Audi A8 D3 Exhaust Gas Temperature Lambda Probe Oxygen Sensor 07L906262B

Product currently unavailable

Part no. 03L253033

Audi A4 B8 A5 8T Q5 8R 2.0 TDI Diesel Exhaust Manifold 03L253033B

Product currently unavailable

Part no. 04L103954D

Audi A3 8V Heat Shield Thermal Insulation Protection Plate Covering 04L103954D

Product currently unavailable

Part no. 05L131525

Audi A6 C8 A7 4G8 2.0TDI EGR Pipe Hose Line 05L131525

Product currently unavailable

Part no. 03L906088AB

Audi A6 C6 Diesel Engine Exhaust Gas Temperature Sensor Pre DPF 03L906088AB

Product currently unavailable

Part no. 80A906265

Audi A4 B9 Exhaust Lambda Probe Oxygen Sensor 2.0 TFSI Petrol 80A906265

Product currently unavailable

Part no. 059906088CP

Audi A4 B8 A6 C7 A7 4G Exhaust Gas Temperature Sensor 3.0 TDI Diesel 059906088CP

Product currently unavailable

Part no. 06L253243L

Audi A4 B9 2.0 TFSI Turbo Exhaust Heat Shield Panel 06L253243L

Product currently unavailable

Part no. 059131515AH

Audi A5 8T 3.0 TDI CAPA Recirculation Exhaust Gas Cooler 059131515AH

Product currently unavailable

Part no. 8W0919529J

Audi A4 B9 A5 F5 Exhaust Gas Temperature Lambda Sensor 2.0 TFSI 8W0919529J

Product currently unavailable

Part no. 06A906262BR

Audi A4 B7 Lambda Sensor Oxygen Sensor Lambda Probe 06A906262BR

Product currently unavailable

Part no. 059131501D

Audi A5 8T 3.0 TDI Diesel Engine EGR Valve 059131501D

Product currently unavailable

Part no. 04L103954AP

Audi A4 B9 Engine Heat Shield 04L103954AP

Product currently unavailable

Part no. 06H145701L-1

Exhaust Manifold Audi A4 B8 A5 8T 1.8 TFSI Petrol Turbo Turbocharger 06H145701L

Product currently unavailable

Part no. 4M0907807BC

Audi Q7 4M Q8 Mk1 VW Touareg Mk3 NOX Lambda Oxygen Sensor 4M0907807BC

Product currently unavailable

Part no. 4M0906262

Audi A7 4G 3.0 TDI Diesel Lambda Sensor Oxygen Sensor Lambda Probe 4M0906262

Product currently unavailable

Part no. 06H145701K-2

Audi A4 B8 A5 8T 1.8 Petrol Exhaust Manifold 06H145701K

Product currently unavailable

Part no. 03G906262

Audi A3 8P Lambda Oxygen Exhaust Sensor Probe Cable TDI Diesel 03G906262

Product currently unavailable

Part no. 8W0919529P

Audi A4 B9 A5 F5 Exhaust Gas Temperature Lambda Sensor 2.0 TFSI 8W0919529P

Product currently unavailable

Part no. 06A959253E

Audi A3 8P Q7 4L A4 A6 Auxiliary Secondary Air Pump 06A959253E

Product currently unavailable

Part no. 03L131512CD-1

Exhaust Cooler Audi A4 B8 A5 8F 2.0 TDI EGR Cooler Engine EGR Valve 03L131512CD

Product currently unavailable

Part no. 8V0253825B

Audi A3 S3 8V Exhaust Tips Pipes Set Left N/S 2.0 TFSI Petrol 8V0253825B

Product currently unavailable

Part no. 8K0906262C

Audi A4 B9 A5 F5 Q5 FY Exhaust Lambda Oxygen Sensor Petrol Engine 8K0906262C

Product currently unavailable

Part no. 8Y0253824A

Audi A3 S3 8Y Quattro Rear Muffler Exhaust Pipe End Chrome Right O/S 8Y0253824A

Product currently unavailable

Part no. 038131513S

Audi A4 B7 EGR Exhaust Valve Cooler Radiator 1.9 TDI BRB 038131513S

Product currently unavailable

Part no. 8Y0253823A

Audi A3 S3 8Y Quattro Rear Muffler Exhaust Pipe End Chrome Left N/S 8Y0253823A

Product currently unavailable

Part no. 06J906262N

Audi Q3 8U VW Tiguan 5N Lambda Probe Wiring Oxygen Sensor Petrol 06J906262

Product currently unavailable

Part no. 059131502B

Audi A4 B8 2.7 TDI Diesel EGR Valve 059131502B

Product currently unavailable

Part no. EXHAUSTS4B7

Audi S4 B7 Milltek Sport Rear Exhaust System Muffler Back Box Double Pipe 4.2

Product currently unavailable

Part no. 059906051F

Audi A4 B8 A6 C6 A8 D4 DPF Exhaust Pressure Sensor Unit Diesel TDI 059906051A

Product currently unavailable

Part no. 03G906262M

Audi A4 B7 Diesel NOX Lambda Oxygen Sensor 6 Pins Plug 03G906262M

Product currently unavailable

Part no. 059131525AC

Audi Q7 4L 3.0 TDI BUG EGR Connecting Pipe Hose Line Tube 059131525AC

Product currently unavailable

Part no. 04L103954G

Audi A5 8T Heat Shield Thermal Insulation Protection Plate Covering 04L103954G

Product currently unavailable

Part no. 5Q0253692A

Audi A4 B9 Valve Exhaust Flap Actuator Gas Valve 5Q0253692A

Product currently unavailable

Part no. 04L906262K

Audi A1 8X 1.6 TDI Lambda NOX Oxygen Exhaust Sensor Probe Cable 04L906262K

Product currently unavailable

Part no. 059131515CC-1

Audi A4 B8 2.7 TDI CGKA Vacuum Cell Exhaust gas Recirculation 059131515CC

Product currently unavailable

Part no. 059131515EN-1

Audi SQ5 8R A7 4G 3.0 TDI CGQB EGR Valve Cooler 059131515EA

Product currently unavailable

Part no. 059131503H

EGR Cooler Audi A6 C6 Q7 4L EGR Cooler Pipe Hose Line 2.7 3.0 TDI 059131503H

Product currently unavailable

Part no. 057253038L

Audi Q7 4L 4.2 TDI Exhaust Manifold Cover Heat Shield Right O/S 057253038L

Product currently unavailable

Part no. 05L906261E

Audi Q2 GA 2.0 TDI NOX Sensor Lambda Oxygen Probe 05L906261E

Product currently unavailable

Showing 298-396 of 529 products

Reliable parts for exhaust systems and emission filters – perfect fit for your car

Durable exhaust components – for maximum performance and durability

Exhaust systems and exhaust aftertreatment systems are essential components of every modern vehicle. Their role is not only to reduce noise but, above all, to reduce harmful emissions, making driving more environmentally friendly and compliant with applicable standards. At Global Parts, you'll find a wide selection of used car parts. for exhaust and exhaust gas treatment systems, for brands such as BMW , AUDI , Volkswagen , Mercedes , Mini and others. The exhaust system in a typical passenger car operates at temperatures ranging from 200°C to as much as 800°C under high engine loads. Therefore, these components must be made of materials resistant to corrosion and temperature fluctuations, such as stainless steel or nickel alloys. A well-designed exhaust system not only protects the environment but also improves combustion efficiency, which can translate into fuel savings of up to 5–7% compared to a faulty system.

How does the exhaust and exhaust gas treatment system work?

Exhaust systems are advanced systems composed of many key components that work together to efficiently remove exhaust gases and reduce their harmful effects. The most important elements include:

Bypass valves – Controls exhaust gas flow, helping to optimize pressure in the exhaust system.

EGR valves and parts – They are responsible for exhaust gas recirculation, which reduces nitrogen oxide emissions and improves fuel combustion.
Secondary air pumps – They support the combustion process by supplying additional oxygen to the exhaust system, reducing exhaust emissions.
Catalysts – They purify exhaust gases by neutralizing harmful substances such as nitrogen oxides and carbon monoxide.
Exhaust systems and kits – Comprehensive exhaust system component kits ensuring optimal engine performance.
Collectors – They are responsible for discharging exhaust gases from the cylinders to further elements of the exhaust system.
Exhaust pipes and tips – They ensure efficient exhaust gas removal and give the vehicle a sporty appearance.
Clamps, clamps, flanges and mounting parts – Mounting elements enabling solid attachment of the exhaust system.
Mufflers and resonators – They reduce engine noise, improving driving comfort.
Exhaust system gaskets – They ensure tight connections and eliminate the risk of exhaust leaks.
Lambda probes and O2 sensors – They monitor exhaust gas composition, optimizing the fuel-air mixture and improving combustion economy.
Thermal shields, connectors and sleeves – They protect exhaust system components from overheating and improve their durability.
Solenoid valves – They regulate the flow of gases in the exhaust system, improving its efficiency. Each of these components is crucial for engine performance, driving comfort and environmental protection. For example, the diesel particulate filter (DPF) installed in diesel engines can trap up to 90% of the soot produced during combustion. In cars from brands such as Audi and BMW, DPF parameters are adapted to Euro 6 standards, which allow nitrogen oxide (NOx) emissions of just 80 mg/km. This demonstrates how precisely these systems must be designed to meet stringent regulations.

Why is it worth taking care of exhaust and exhaust gas treatment systems?

Regular maintenance and replacement of exhaust and exhaust aftertreatment system components is essential for efficient and environmentally friendly engine operation. Neglecting these systems can lead to:

Increased exhaust emissions, which may result in failure to pass the technical inspection.
Damage to key components such as catalytic converters or DPF filters.
Decreased vehicle performance and higher fuel consumption. At Global Parts we offer genuine used car parts , which undergo rigorous quality testing, ensuring reliability and durability. Taking care of your exhaust system isn't just about the environment, it's also about saving money. For example, a leaky muffler can increase fuel consumption by up to 0.5 l/100 km. With an annual mileage of 20,000 km, this translates to an additional 100 liters of fuel, a cost of several hundred zlotys.

How to choose the right parts for exhaust and exhaust gas treatment systems?

When choosing parts for the exhaust system and exhaust gas treatment systems, such as mufflers, catalytic converters or particulate filters, it is worth paying attention to:

Vehicle-specific fit – Every car make and model requires specific solutions. At Global Parts, you'll find exhaust and aftertreatment components perfectly matched to BMW , AUDI , Volkswagen , Mercedes , Mini, and more.
Technical condition – Make sure components are free from damage, corrosion and cracks.
Emissions Compliance – Ensure the parts you choose meet current emissions regulations.

To make the selection of parts easier, below is an example table of compatibility and wear symptoms.

Element	Typical signs of wear	Application/Compatibility
Silencer	louder engine operation, metallic vibrations	most BMW, Audi, VW models
DPF filter	power loss, engine error message	diesel engines, Euro 5 and Euro 6
Lambda probe	higher fuel consumption, uneven engine operation	all petrol and hybrid types
Catalyst	characteristic smell of exhaust fumes, loss of power	vehicles with emission standards from Euro 3 and above

Why choose used exhaust and exhaust aftertreatment system parts?

Used car parts This is an excellent solution that allows you to save money while maintaining high quality. By choosing used exhaust systems and exhaust aftertreatment parts, you gain:

Lower costs – Used components are much cheaper than new ones, but offer equally high quality.
Ecology – You support recycling and reduce the amount of automotive waste.
Wide selection – In our store you will find components for the most popular car brands.

How to take care of the exhaust system and exhaust gas treatment?

To ensure that your exhaust system and exhaust gas treatment system continue to function efficiently for years to come, it is important to remember a few rules:

Regularly check the condition of the DPF filter and catalytic converter - clogging them can reduce the vehicle's performance.
Keep exhaust pipes clean to avoid corrosion.
Avoid short journeys, which may cause the exhaust system and its components to underheat. In case of damage or wear, you will find the right used car parts at Global Parts that will restore full functionality of your exhaust system.

FAQ - Frequently asked questions about car exhaust systems

Question	Answer
What is the main purpose of the exhaust system?	The exhaust system is a system of pipes and components whose task is to remove and purify exhaust gases, reduce noise and support engine operation.
What does exhaust gas purification system mean?	It is a set of components, such as a catalytic converter, DPF filter and EGR valve, whose task is to reduce harmful chemical compounds in exhaust gases and meet emission standards.
What is a lambda probe used for?	The lambda sensor monitors the composition of the fuel-air mixture and sends data to the engine control unit, which allows for optimal combustion.
How to recognize catalytic converter damage?	Symptoms include a loss of engine power, a check engine light and a characteristic exhaust smell.
Does a DPF filter fit every diesel?	No, DPF filters vary in design and parameters. They must be matched to the make, model, and emissions standard (e.g., Euro 5, Euro 6).
How often should a muffler be replaced?	Under normal operating conditions, an exhaust muffler can last up to 80,000–120,000 km, but its durability depends on the quality of the materials and driving style.
Are the exhaust system parts used safe?	Yes, provided they are verified and come from a reliable source – just like in the Global Parts store, where each part undergoes quality control.

Summary: Exhaust Systems and Exhaust Gas Treatment at the Global Parts Automotive Store

Exhaust systems and exhaust aftertreatment systems are the foundation of modern vehicles, combining ecology, efficiency, and driving comfort. By maintaining their technical condition, you ensure reliability and compliance with applicable emission standards. The Global Parts automotive store invites you to browse our wide selection of original used car parts . Whether you're looking for car parts for BMW , Audi , Volkswagen , Mercedes, Mini , and others, you'll find them at competitive prices. We strive to ensure every customer finds the right parts for their car, and if you have any questions or concerns about selecting the right components, we're happy to help! Please contact us – we're here to help! For more information and interesting facts, visit our automotive blog .

used parts mercedes used car parts audi used car parts cheap car parts audi auto parts volkswagen genuine parts spare parts bmw exhaust & emission systems mercedes exhaust & emission systems mini exhaust & emission systems audi exhaust & emission systems volkswagen exhaust & emission systems