Opjose,

I totally agree with all that you have written. Went through all of that and added and reduced nitro content, changed mufflers (stock and pitts), tried larger fuel lines, swapped out for tried-&-tested tanks etc etc. The only thing I didnt try was replacing the engine and changing to synthetic (I used to run castor then). The 75ax was an engine I didnt fully run-in. Anyway, with the FS91SII, I corrected all of those things, some of them basics and dropped the tank height and I got it reliably working. So much that when I tried to do a harrer roll at 50 ft and the airplane rolled half way through and headed for the ground, I was actually more concerned for the engine than the airplane (I was at 3D throws, I leveled out at full throttle just at the moment it hit the ground- actually heard a whack when it did that, was pointing at the pits, flew out first, did 1/2 circuit, landed with shaking hands and found that everything was just fine)

Ameyam