Are you running the Keihin or Keihin knock off power jet carb? If so have you cleaned the carb to include the air ports in the mouth of the carb? What I have found is that when the power jet function is used it sucks fuel/oil into the air tracts and plugs them up and they run like crap. If you haven't gave it a good cleaning, try it and if it does work for you plug the power jet line and go up on your main jet or just replace the carb. I've got a pile of them if anyone needs one ...
WPSA 90 CVT #2
07' APEX 90MXR
Probably not the fastest, but hopefully fast enough...