I have an 18 M6 WB. Still under warranty not sure if that is an issue. If not @greasy can advise you as he has a 840whp M6. If so for me Barton shifter, Fastman TB, Pedal Commander, Lowering Springs, 190° Tstat, Legmaker CAI, and biggest was 315 555r2's. More air, ability to put the power to the ground, better throttle response, and no wheel hop have made this a whole different car thus far. You can definitely get 800+WHP on a pump gas build as well.