The milder of the two systems available for the S4, Billy Boat Performance Exhaust Audi S4 cat back exhaust is manufactured using only the highest grade T304 stainless steel materials available. CNC mandrel bent 2-1/2” tubing is used throughout the entire system for a smooth uninterrupted exhaust flow for added horsepower and torque. Hand fabricated mufflers incorporating B&B’s unique Purge Resonance Technology (PRT) give the S4 a distinct exhaust note.

The simple in design yet unique in theory PRT mufflers allows for a deep sporty note on hard acceleration but offer a mild tone while cruising without the unwanted interior resonance. To finish the system off B&B uses a quad tip design with 3.5” round double wall tips for a look that is pleasing to any enthusiast’s eye. With the system being an after cat design it is 50 state emissions legal and is backed by B&B’s limited LIFETIME WARRANTY.