ThunderMax ECM With Integral Auto Tune System For Harley M8 Softail 21-24ThunderMax ECM With Integral Auto Tune System For Harley M8 Softail 21 24 Are you ready to get every ounce of horsepower out of your M8 softail? This tuner will do exactly that. Every degree and a half of throttle; every 256 RPM, there is a fueling point that is automatically adjusted. That means more control and a smoother running engine. With the built in barometric sensor you never have to think about ambient air changes. WideBand O2 sensors