You set the rpm that you want the 2-step to engage at. Step on the brake, hit the momentary switch to activate it and floor the gas. Mine is set at 2800 rpm. When the motor hits 2800 spark is cut to every other cylinder and they alternate so it won't wash the cylinder walls. The rpms will stay at what you have them preset for. Unburnt fuel will enter the exaust and ignite causing the turbo to spool up. When you let off the brake pedal all cylinders begin to fire. When a car is using a 2-step it sounds like it is banging off the rev-limiter.