So what difference does a dyno tune make? Well, a tune makes a huge difference. With the valves open and the only addition being custom tuning from BrenTuning output rises just under 100 horsepower at the wheels to 451 horsepower and 406 lb-ft of torque. The torque curve from 5200 rpm until redline does not drop nearly as much as it does with the factory AMG tune. This has a big impact on horsepower up top and the peak power figures.
With the addition of SLS Black Series spark plugs (1 step colder), custom airbox modifications, and a new dyno tune increasing the rev limiter peak power sees an additional increase making use of the extra revs for a 30 wheel horsepower gain to 481. Torque gains are seen through the entire curve.
Essentially, with minor bolt ons and custom tuning you see a C63 go from 356 to the wheels with a full exhaust system to 481 to the wheels for a gain of 125 wheel horsepower. The M156 responds very well to tuning as we all already know and Mercedes left quite a bit of room in the motor to not step on the toes of the big boys in the lineup.