Welcome to the finest catback exhaust for the B7 Audi S4 on the market. The AWE Touring Edition Exhaust for the B7 S4 is a direct bolt on catback system that not only transforms the rear end of the car with its menacing quad tips, but also turns heads with a deep muscluar bass note. Each cat back system features an H-Pipe crossover tube at the front to maximize exhaust scavenging for maximum power, as well as to take a harsh edge off the exhaust sounds. Tubing diameter for the entire system is 2.25". This is a deep bass tone, no matter how you cut it. Dyno proven for legitimate power gains of 14.2 hp and 14.8 lb-ft torque corrected to the crank on our in house Mustang AWD dynamometer, the B7 S4 Performance Exhaust is a must have for any B7 enthusiast.