It would be good to see an AFR against Boost plot really to see what is going on, certainly worth a test to add 2 lb of boost and see if the fuelling starts to level out.

max of 4mm preload on the actuator, the rest to be done by jetting the amal valve, if the boost is tailing off it may explain it, so if you can get it to hang onto some extra boost at high RPM the fuelling may correct.