sparks rev pipe

[cdrookie]

talking with my buddy this weekend and he said he got one of the curtis sparks rev pipes for his yfz. he can't keep the machine running properly from one ride to the next. he called sparks and is running their jetting specs. it has a K&N with the lid removed but is otherwise stock except for the exhaust. he said it'll run great one day then he'll get smoked by everything on the strip the next(he does local dirt drags). it always ran consistant before.

was just wondering if anyone else has any experience with these pipes?