RE: rich or lean gas?
tiktock, I don't have a DA but my FPE had the same symptoms when I first got it. It ran good on the ground but airborne it sputtered and went rich. The velocity stack was in the airstream and the mfg suggested it might be creating a vacuum causing the engine to go rich. He suggested I remove the velocity stack, which I did so the carb would be inside the cowl, and the problem went away.
It worked for me.
Larry