The Mercedes S 250 CDI 204hp (W221 - 2005 - 2013) produces 204bhp and 500Nm in standard form. Our Stage 1 ECU tuning file raises output to 230bhp and 560Nm, a gain of 26bhp and 60Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.