I had lots of little issues with the pa, one being pap wouldn't warrant the warranty cause i brought it second hand, even though it only had 4 hours on it. I wont go into detail..
I may of had a few more hours than that but the needle valve was worn ( little rubber on the end) and it was letting in to much fuel causing it to get high compression (intermittently).
Sounds like the same problem that you are having, you can get a carb kit from sky dragons, and it should come with the needle valve.. You may have a different problem but defo sounds like that to me..
Its a bastard when it kicks back at you nearly took my fingers off !!
I have now got a Bulldog moster and am now a happy bunny !!!