All it does is over ride the Cruise Control or speed limiter. Nothing special TBH.
Want you want to do is stick the car onto speed limiter, second gear get to 40mph and set it. Then when you have a prick behind you coming out of a 40 into national speed limit, floor the loud pedal and the car will just fly.
Basically you are just sat below the 5k mark so when you boot it you hit cam and go. WORD OF ADVISE HOLD ONTO THE WHEEL