I have the PWK on my '03 CR. I like it, it revs smooth and cleanly. Cant say that there was any real performance gain, other than no hiccups or jetting troubles. I got mine from CPW, pre-jetted for my bike. I didnt change much except for the main and needle clip. I believe that I have a 175 in it now. It fit fine, didnt have to do any mods. Jetting changes are easy, needle changes are super easy compared to the Mikuni. The only thing I do to make it a little easier is remove the 3 bolts on the case guard, this gives you a little more room to work. Dont remember if you asked or not, but other mods include, V-Force, SST pipe, Ti silencer, Boyeson exhaust flange. Any more questions, ask away. Hope this helped.