Catless Downpipes For Audi S6/ S7/ RS6/ RS7 C7 4G 4.0 TFSI QUATTROHigh Velocity Flow: Catless Downpipes for the Audi 4. 0 TFSI V8 Engine Who Its For: Engineered for Audi S6, S7, RS6, and RS7 owners running the 4. 0 TFSI powerplant who are ready to eliminate the primary bottleneck in their exhaust tract and let the twin turbos breathe. The Symptom: The factory downpipes on the 4. 0 TFSI are designed for extreme emissions compliance and cabin silence, which comes at the cost of performance. The stock units feature