A FMIC will help some, but it won't change the compressor map of the turbo. fact of the matter is no matter what supporting mods you have, the turbo cannot flow more CFM past 18 psi. Go past that, you start making excessive heat, as well as overspeeding the turbo.
Hence why Stage 3R comes with an upgraded turbo/manifold.
Also, the reasoning for upgrading the WGA(AGP or whatever) is to make the turbo hold more boost to redline, not neccesarily to increase boost. If you can hold 16 to redline or even to 5200-5500 rpm, and you'll have one quick SRT-4.