I guess there's a lot that could be wrong here, especially since my plane crashed and spent the night in a corn field; the engine did look very clean however - nothing in the carb.

So the 55AX is running poorly at mid throttle- anything over idle and under full throttle. Sounds bogged down or something. I've tried changing plugs and fuel and nothing changed.

I tuned her up with a 13x5 prop and got about 9000rpm, though the engine was even sputtering a bit when I was tuning. After a flight I switched to a 12x8 prop and found 12000rpm. I went to fly and it wouldn't rev up, so I pulled it into the pits and on a hunch leaned the high speed 2 clicks and the rpms shot up, and was back up to 12000rpm.

I flew a few circuits and landed, the rpms never seemed high enough in the air. I re-checked on the ground and was only getting 10000.

The biggest problem is at mid throttle though; it's not enough to move the plane on the ground, and sometimes sounds like it wants to choke out.

I'm going to check for leaks and clean out the carb. Any other ideas/suggestions?

The LHS said he had a 75AX which did the same - idled great, top end was great, but middle throttle it gurgled. He said some engines are just like that. I refuse to believe the 55AX is going to run that way with nothing wrong with it.