last year the trimmer ran fine, this year i'm having a few issues with it not running as smoothly as it should. cleaned air filter, adjusted the carb a bit, and got it running a little better. however i'm having trouble getting it to idle consistently. it either wants to die or spins with no throttle. I can adjust it and get it idling right, then use it awhile and its back to either dying or idling high, adjust it again, use it some more and same thing. when i turn it upside down to trim half the time it starts idling higher. seems to have no relation to how much fuel is in the tank either. last year i had to run fuel with ethanol through it, this year i found a station that has ethanol free so i switched to that this year. where should i begin? new carb?