I'm having the very same issue with my 2001. Did you ever figure out the issue? Done everything you did as well as new intake boot. Still no luck1999 Prairie 300. Starts quick, idles great. Goes fine until about 12mPH(1/4 throttle) then it will spit and sputter if you hit the throttle further. Feels like it wants to die but doesn't. If I put the choke on 1/2 way it will go pretty well until 3/4 throttle then to go wide open I have to have choke on full. If I stop with the choke on it will die. I checked carb didn't see anything wrong. Put new carb on it and runs the same. Changed the fuel filters in the gas tank as it seem to be starving for gas. No change. Air filter seems very clean. I have had this wheeler for many years and it has always ran this way. Just get tired of having to move the choke to go faster. Any ideas would be appreciated.