Quick view Fabspeed Tuning Mercedes-Benz M278 4.7L Bi-Turbo XperTune Performance Software $1,895.95 Performance ECU software upgrade improves horsepower, torque, and driving characteristics of the M278 4.7L V8 BiTurbo Engine by reprogramming various sensor inputs, air/fuel ratios, and boost pressure. ... Add to Cart Add to Cart Add to Wish List Add to My Wish List Create New Wish List