The Audi RS6 4.2 Biturbo 450hp (C5 - 2002 - 2004) produces 450bhp and 560Nm in standard form. Our Stage 1 ECU tuning file raises output to 520bhp and 725Nm, a gain of 70bhp and 165Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.