OK my buddy has a 05 636 and ordered a full race exhaust for from yoshi i beleive. well he went ahead and took the old exhaust off then comes to find out it doesnt ship till the 30th or some shit. so he put his stock stuff back on and he says it isnt running right. when he gives it full throttle it is not goin as fast and he says it stops pullin at 9000, but the revs will get higher. any ideas what the problem might be? i think it might be the little butterfly thing in the exhaust stayin closed but i dont really have any idea.