Pylonracr, thanks for the quick reply. I found I only had 1/2 gal. of CP 15%. I tached the .61 with the APC 11x7 and stock muffler,and new OS #8 plug. Got 12,240 on the ground with 2,800 idle. Second run was with the baffle removed. Had to richen it up about 1/4 turn but got 12,600 on the ground and idle @23-2400 rpm. Sounded very healthy. As far as oil in the fuel I was using CP 15% and adding 3oz Klotz Benol to a gal.of fuel.Seems most fuel doesn't tell You what they use. Do You use higher ratio nitro? If so, what do You use? How do You determine if You need a head spacer/shim? We are at 42' above sea level here in this part of Fl.Will Dubs Red Jett Muffler make a bigger difference? Sorry for all the questions, but I want to get this right the first time. Thanks, TJ