I had the same exact problems you are having with my RTF Alpha. It was a huge PITA to tune. have you checked your fuel lines? i had small pin sized holes on BOTH of my lines going from the tank and i replaced them. Since then i haven't had any problems. I noticed fuel around my motor and on the table where i tuned the engine. I checked everything and noticed some leaking around the tank/muffler so i changed them out. Also, the lines that came with my plane were very long, noticed some improvement by shortening the line going to the muffler.