RE: Tower 75, sullivan onboard glow
I don't think an onboard glow driver is going to fix that. Mostly, the onboard glow is to help inverted 4 strokes idle better, or act as an igniter for starting (for engines totally enclosed without having to poke a hole in the cowl). The problem you are experiencing sounds like the low speed mixture is too lean, or it's underpropped. If it is more prominent in the air than on the ground, it's probably too lean. The weight and momentum of the airplane actually allow the prop to spin faster in the air (at level flight or in descent) because there is less resistance on the prop.
If you can run WOT till the tank goes empty, you have enough pressure. Unless the engine is on its last leg and all worn out, it doesn't take much pressure in the tank to feed the engine. The pressure in the fuel tank needs to be just barely more than atmospheric.