The Mercedes CLS 53 AMG 435hp (C257 - 2021 ->) produces 435bhp and 520Nm in standard form. Our Stage 1 ECU tuning file raises output to 460bhp and 620Nm, a gain of 25bhp and 100Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.