Hey , welome to both of you !! Don't know if shop was to do more than clean and sync carbs , but not sure what exhaust "boots" you're refering to, a two stroke doesn't need bakpressure to run. It is for max power. If they THINK that's the problem , they have no clue. More info would be helpful in diagnosing problem. Jetting , TORS , air cleaner , what you have tried , etc. If the shop was supposed to make it run properly and didn't , thats a problem.