Boost controller

I figured out my last problem, but I still dont understand something. I have a Hahnracecraft stage IV super 16g turbo, and everything that came with it, I also have a portfueler. Ive got everything I need to run about 21-22 psi. I have a greddy profec type s boost controller that is able to control up to 43 psi or so. Now, when I turn the knob all the way on this controller and max out my full boost, I only read about 20-21 psi on my gauge...but the adjustment knob wont turn any further. If the controller can control 43 psi, why is the knob as far as itll go and ive only gotten up to about 21 psi...is the controller designed to adjust to the car psi potential, based on mods? Does it know that I still need other things b4 it will allow me to up the setting, to safeguard my engine? Whats going on...lol, completely confused(all work was done pro, rebuilt block w/ forged int.) The person who sold this car to me said that the whole mod setup is capable of up to 400 hp(I checked it out on the company website, and it is). More with an upgrade from that company of coarse. He said the ignition system on there now would support up to 22 psi or so, does this mean if I improve it, ill see more boost? Whats holding me back? Thanks!
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HahnRaceCraft Stage IV super 16g turbo w/ side mount intercooler - Hahn turbo manifold - 240cc injectors - Hahn Portfueler system w/ intake spacer, secondary fuel rail w/ 400cc injectors - 1:1 aeromotive fuel pressure regulator - fully programmable fuel controller(pretuned) - walbro 255lph fuel pump - Hahn fuel mapper - 3000gt bov - JE pistons(8.6:1) - Total Seal piston rings - Eagle rods - AEM synthetic filter - C & R racing radiator w/ high flow fan - Hahn 3'' downpipe & cat - THermal Engineering 3'' cat-back - Clutchmasters stage IV clutch - Eibach sportline progressive lowering springs - Front Eibach offset bushings(camber adustment) - KYB GR2 struts - Front & rear strut bars - Lower rear tie bar - GReddy profec type s boost controller - autometer boost & electronic fuel pressure gauges - Apexi universal turbo timer - Pioneer mp3 head unit & speakers - odyssey PC680 battery - Front Powerslot drilled & slotted rotors

Well, I did some research, and found the problem. I have a hahnracecraft portfueler system, extra fuel rail, more inectors, ect.

If I want more boost im going to have to get bigger injectors on the portfueler rail, and prob another tune...but thats what it was.