plain and simple, the stock pipes suck, and are HUGE robbers of power even when they are clean. I just got the expansion chamber from spooky tooth, and man...what a HUGE difference in power. It has more bottom end, and alot more mid range power now. it definitly has more top end speed, but i have no way to tell for sure because i don't have a speedo.
Everyone says that the spooky tooth pipe is loud, but to me, it isn't that loud...sounds like a chainsaw.
I also added a high flow air filter so now my motor can breathe in and out alot better. i did notice a big difference in the way the motor revs now...it revs a lot faster than it did with the stock pipe.
I also threw on a boost bottle just for kicks, and i really didn't notice that much of a power gain, but the motor does seem to run smoother.
i'm using the little 50 c.c. slant head motor while most people are running the bigger 80 c.c. motors.