i just ran into the same problem today, been running fine since i got it, compression is fine
it has
fmf fatty, SST silencers i think (unmarked, just what i was told)
pro design intake and filter with outerwear filter
pro design jets (so i was told)
boost bottle
i just had the local shop tune it in may and then yesterday i went out,
let my friend ride it up a medium hill climb , i got on it and it was pinging pretty much at the powerband or shortly after (which may actually be all the way up there since once it hits its gone!)
but other thing is this was a fresh tank of gas (i buy 93 octane i think, its the highest stuff at this Turkey Hill nearby) and i use super-m stuff, synthetic 2 cycle racing oil (5 gal gas : 16 oz oil, 40:1 i believe ....always bought from there before, never a problem
my other friend whos never owned anything with a motor besides his car says to richen it ... i dont think thats the problem
i have all stock insides excapet the impellar.
could it just have been hot from the hill climbs? althought on the way home its a pretty far flat stetch it shoulda cooled down, i rode home under the powerband just to be safe