The Audi S6 4.2 V8 340hp (C5 - 1999 - 2004) produces 340bhp and 420Nm in standard form. Our Stage 1 ECU tuning file raises output to 360bhp and 450Nm, a gain of 20bhp and 30Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.