The Mercedes CLS 350 CDI 258hp (C218 - 2014 - 2018) produces 258bhp and 620Nm in standard form. Our Stage 1 ECU tuning file raises output to 290bhp and 690Nm, a gain of 32bhp and 70Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.