I'm gonna take a shot at it,mine didn't run so good when i first got it and the high speed was as rich as it would go against the stop but it still didn't seem right.Saturday a guy listened to it and at full throttle,pinched the gas line just before the highspeed setting and it didn't run very long then died,it's supposed to rev up a little before it dies,he jumped the factory stop about 1/2 turn at full throttle and it sounded great,then pinched the line and it ran longer this time then revved up a little,he was satisified.
This may or may not help but at least it's worth a try