It is possible to do a pretty darn good closed loop setup for SOME uses
My favorite is a tuned exhaust (for quiet operation and increasesd power)
add to this SOME type of balance correction using the exhaust pressure which increases fuel flow as the exhaust goes resonant.
"HUH?"
I have measured this many times and in all cases , I found that as the power increases the need for fuel increases sharply. Note I did not say as rpm increases tho typically the rpm does increase.
Where many modelers lose it -is by leaning out the mix till rpm is maxed in level or slightly diving flight
The engine may make more rpm -but the load is lower
as soon as the load is increased . the engine goes lean. This situation is common as fleas on a hound.
The so called pressure regs sold by sme outlets are yet another botch up
I measured the pump to pressure readings on all the early OS pumps Perry etc., and always got the same result
max pressure at lowest rpm.
Worthless
The fuel DEMAND relative to power goes up very sharply
On Walbro setups - the easy fix is to insure that the reg diaphragm does not see a decrease in vent pressure as the engine goes to full power
Also the tank should flow as easily under high demand as under low demand
I believe in a forward facing vent line and no filters in the lines.