The S7 with that pipe should be a pretty fine combo when it comes to torque and speed, what gearing do you have ? what Nitro % and plug are you running ? what do you want to bottom end for ?

Also how old is your clutch ?, I`ve heard the alloy shoes when they get a bit warn will develope a burr and drag....and if they are dragging they will seriously hurt the buttom end performance.

TM