a fuel pump will feed the fuel at a constant pressure, you then adjust the needles to get the flow to where you want it (because igf you pump the fuel at higher pressure it's going to force more fuel through the same size space which will make the engine run rich), the problem be, in my mind that the power needed to run the pump would be to much to have any sort of good runtime, planes, particularly planes used for 3D flying use fuel pumps so the engine doesn't stall under high load, you could run the fuel pump off of say the primary shaft on the transmission, that would give a variable fuel pressure throughout the RPM range, of course then the idle would suffer (would lean out at idle because there would be no fuel pressure because the pump would be driven off of the transmission, not the engine), it is a thought however and may be worth a look if you really wanna get rid of lean tank and are willing to do a bit of work.