It sounds like a plugged fuel line from the fuel tank to the carburator. Are you using fuel stabilizer in all of your gas, good quality 2 stroke oil and running the unit out of gas when you are done for the season. If not that is your most likely problem and cause. Remove the fuel line clean and/or replace it and that should solve your problem provided the carbuator isn't clogged also.
I have a 350BT and bought the flare nozzle for it. I think it is will worth the money. It increases air velocity and give you a more precise air flow so you can better control where the leaves go.