High Flow, fully polished stainless steel downpipes - Audi S4 B6 / B7 2004-2008




Billy Boat downpipes will only fit Billy Boat and APR cat-back exhaust systems. In testing a full Billy Boat exhaust produces gains of 25hp and 35lb-ft across most of the engine power band. Throttle response is also greatly improved.

The option of no catalytic converters and high-flow catalytic converters is available. The high-flow cat system replaces the 4-cat factory setup with a pair of metal matrix catalysts, providing extreme increase in flow over stock. Select your option below.


Please specify whether your S4 is 6 speed or TIP when ordering.