APR's B6/B7 S4 Exhaust is offered as both a full or as a catback system. The catback system is a complete stainless steel, mandrel bent, cat-back exhaust. The exhaust is a dual 2.25" system that begins at the factory downpipes and continues to an innovative center muffler. The exhaust then splits and each mandrel bent pipes goes to its own muffler with a 3.5" (90mm) bevel-cut, round tip for the B6 S4, or dual 3" (75mm) for the B7 S4.
This exhaust is very quiet and simply changes the tone of the exhaust to a deep, unobtrusive sound. With TIG welding, fully stainless construction, and CNC'ed hangers, you will not find a higher quality system on the market.
A set of downpipes is also available for the S4's. This system replaces the 4-cat factory setup with a pair of metal matrix catalysts. APR downpipes will only fit with an APR catback system. In testing, a full APR exhaust produces gains of 25hp and 35lb-ft across most of the engine powerband. Throttle response is also greatly improved.