the FMU (rising rate reg) is correct for a turbo application, it just may not be able to do more than a single stage of boost. on the fuel system, the fmu puts the a/f somewhat close to where it needs to be, then the power commander adjusts the fuel to put it exactly where you need the a/f t be. when you up the boost like 5 psi for example, you may need a higher RATE of raising the fuel pressure to maintain the same a/f as well as some altering of the power commanders tune.
for example (rounded numbers to make eisier example), if you had 100 units of air molecules and needed 20 units of fuel at a particular setting, then upped the air flow to lets say 133 units of air, you might need 29 units of fuel. the second stage has 33% more FUEL, while it needed ~45% more fuel for the air.
but now the GOOD news... you do have a couple of options if you want multiple stages of boost. the first is you run TWO power commanders and set up the second to read BOOST instead of throttle position. fyi; the PC maps are rpms x throttle position. so one would tweak the fuel according to the throttle, the other according to boost. have not done myself, but i guess a few shops do it regularly. i think i may give it a shot too.
option two: there is a new module that PC made that will read boost, and then be able to make adjustments accordingly. AHAB for SH.org has one, but i have not heard any updates on it being installed yet and the sort...
for the last statement, if you ran 2 stages and ran the boost levels similar enough, it MIGHT work without doing anything fancy like the above ideas. if you wanted like 8psi and then up to 10psi, the tunes MAY be similar enough that the FMU would be able to compensate for it alone without another fuel tweaking device. once again, i have not done this myself, but it would SEEM like it could work IMHO.
good luck and BOOST!!!!!!!!!!
