I have a APC 11x5 prop on the engine. A OS A3 glow plug and useing Morgan Cool Power 10% for fuel. I broke the engine in on a test stand with the above fuel and no added oil, not overly rich as to 4 cycle but as rich as I could with out 4 cycling. I did this by intermittantly running at 1/2 throttle, full throttle, idle. Shut off, cool engine and repeating until I had run 2 tanks of fuel thru it or approximately 24 oz. I just checked the engine by taking the glow plug out and I can feel the tightness at the top of the stroke. I had the muffler off yesterday and I do not see any evidence of scoring thru the exhaust port. The engine has very good compression with the glow plug in. I have tried several different glow plugs including a Fox with idle bar. Everything I have done has not seemed to help very much. Also I might mention the temperature outside yesterday was 40 degrees and the humidity about 30 %. I did run and fly this airplane last fall when the temperature was at least 70 degrees with pretty much the same problems. I have had several guys at the field try to adjust the carb, change & glow plugs all to no avail.