BMW Exhaust systems are designed for high performance while still meeting noise and emissions restrictions. Those three requirements are sort of mutually-exclusive, meaning there's a lot of engineering that goes into the BMW exhaust. To start with, there's the choice of exhaust pipe material. On higher-end cars, you'll find stainless steel, while mild steel is used on lower models to save money. Then comes the method of fastening everything together: most OE BMW exhaust systems are welded rather than clamped to create leak-free joints.

Where the real challenge lies is in making the mufflers and catalytic converters as free-flowing as possible while still getting them to do their jobs; namely, reducing noise and cleaning up the exhaust gasses, respectively. The stock BMW exhaust does a pretty good job, too. But if you don't mind a little louder exhaust, consider replacing your factory BMW exhaust with an aftermarket high-performance exhaust. You'll build more horsepower, your engine will rev more freely, and you'll get the sweet sound of a low-restriction exhaust system.