Charlie P.

When you're nose up you're pumping fuel uphill. If the diaphragm is shot or holed that will show it. It also shows if you're tuned overly lean. Try backing off (counter-clockwise) the Low needle 1/8th of a turn. The fact you're dead-sticking in level flight could also show you're overly lean. Especially if it runs otherwise well and then just stops suddenly. Too rich usually runs poorly . . . but runs. Gently tighten the HighSpeed needle and try backing it off two turns. 1-1/2 to 2 turns is the "factory reset" for the high speed setting.