Background... OS-160FX, Slimline Pitts Muffler w/straight pipes (no rolled ends). Very wide adjustment range. Constant dead sticks, poor run around mid range, got hot died.
I read all the posts, and installed large fuel lines, Perry Pump VP-30. Ran great on Ground. Flies good once in a while, but still dead stick about every other flight. Usually quite
hot.

Pulled tank, replaced lines, checked for leaks/pin holes found none. This time I ran it with cowl off as we were starting to think I just needed more airflow. Noticed that as I
stat leaning the high end, and get probably 800 RPMs from peak, there was a LOT of air in the carb line, so if allowed to continued would lean, get hot, and die. I let it cool, and ran it again.
there is no noticeable air into the pump, but air all the way from the pump to the carb. I replaced the large lines from the filter (before pump) all the way to the carb, with medium line, and zip tied all
connections. Ran it tonight, and it seems better, but at full throttle, after a few seconds at about 500 RPMS before peak, it will still pump a lot of air into the line at the pump.
The only thing I can think is: either the needle valve is leaking, but then I should not have air between it and the pump. Soooo Must be the pump. It is new, and I have only adjusted it about 1-2 turns in or out, not even close to
the limit either at end.

Any thoughts would be very helpful.

Les