You take out the muffler and check for carbon build up blocking the exhaust? Clean the spark arrestor screen on the muffler?

When you took the carb apart, did you use force air to blower dry the parts?

Might first thought is a vacuum leak, all the jug and crank case cover screws are tight right? second thought how about compression? Blowers can wear out and engine quickly, takes alot of torque to blow air. after that MY guess would be carb. diaphramn gone south. Might try a new 8 dollar carb. kit.

I had the same problem with mine. Replaced spark, air and gas filter. Cleaned the exhaust (the exhaust was clean though). The gas bulb broke in the process, so I replaced that. It turns out to be the gas line in the tank had corroded holes in it.