"Pro Circuit Works with Factory Sound silencer Fit: A / Overall Rating: A Comments: Picked as the head honcho by one tester, the PC comes to life from the first blip of the throttle. Bottom is superior overall and pulls harder while exiting corners. As the revs start to climb, it keeps pulling until screaming its brains out way up top."
this is right out of dirt rider magazine. they say PC is the best for the yz