I have a raptor 30 with an os32 abc engine I'm not sure of the muffler as I bought the package used. The previous owner said he ran less the 2 gallons of fuel through and I believe him as heli. and engine looked like brand new. I ran 5 gallons of Omega 15% cool power no problem plenty of power hovered around 1/2 stick on transmitter and had good forward flight. On my 5th gallon of fuel I noticed less and less performance out of my heli and i started eating Glow Plugs I"ve tried hanger 9 and os no.8 top of the line plugs or so I think. Anyway I can't get off the ground until half a tank or more of fuel is used. I've also tried throttle and Pitch curve changes with no results. I have also switched to 30% nitro with no results. Removed engine disassembled. noticed no real "TIGHT" spot near top dead center of engine with head off. Should you have one on an abc engine? and found No excessive scoring on piston or sleeve and very little carbon on exhaust side of piston. I would appreciate any help or comments.