MagnaFlow SYS C/B 04-05 Audi A4/S4 4.2L DSRThe MagnaFlow Audi S4 Sport Series 16586 enhances your 4. 2L 2004 2006 Audi S4 with an aggressive character that is sure to help you stand out from the other Audi S4 you encounter on the street. With its 2. 5in. diameter fast flowing mandrel bent main piping that passes through 4 Straight Through mufflers before ending in a Dual Split Rear exit with 4in. Polished Welded Double Wall Angle Cut Rolled Edge Resonated tips, this dyno proven Audi S4 exhaust