Man....sounds damn near exactly like my problem...but my problem is only at WOT, idle, half to 3/4 throttle shee revs fine,...just at WOT shee backfires & spits, sputters....See my post about 'Cracked Reeds' in this section of the forum. I'm at a loss,...I'm going to try swapping the coil out, and maybe my stator--but it's damn near brand new still. Before when my stator went out there were no warning signs, no problems. Just wouldn't start after I shut it off after a normal ride until it was replaced. So if you figure yours out, let me know what it was because it could be the exact same problem I'm having...