I just changed my 99 wr400 to yz timing. And I gotta say, it really sucks. Has NO low end power at all. I used to be able to tap the gas and pull, the front wheel up all the time, now it won't come up even if I pull. It may be a bit faster at WOT but I seldem ride at WOT. I mostly trail ride. You can hear it sucking under the seat, sounds way different. Maybe I did something wrong. The are two things I am going to check. First the air filter is pretty dirty, so I am going to clean it. Second I haven't cut the grey wire yet. Would either of these make a HUGE difference? If that doesn't make a HUGE difference I am switching back.