The Ford Mustang GT 5.0 V8 421hp (2015 - 2018) produces 421bhp and 542Nm in standard form. Our Stage 1 ECU tuning file raises output to 441bhp and 562Nm, a gain of 20bhp and 20Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.