The Mercedes S 500 - 388hp (W221 - 2005 - 2013) produces 388bhp and 530Nm in standard form. Our Stage 1 ECU tuning file raises output to 408bhp and 570Nm, a gain of 20bhp and 40Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.