Need help. Just rejetted dads grizzly 450 stock exhaust, uni filter stock everything else. Used a dynojet kit w/a 124 jet and it seems to be lacking power and backfiring on deceleration. I went from 2.5 turns to 2 turns out on the a/f and it helped. It also Is blowing smoke, smelling real bad and occasionally stalling under idle. It is starting right up though and running at a higher idle with the choke on no matter if the engine is hot or cold.