Yes most afpr do increase fp under boost. At least my paxton one does. My base pressure is around 40 and I see almost 50 under full boost. Its almost a 1 to 1 ratio.
As for running 55-60lbs vacuum off, don't do it. I mean it will run really bad down low and you will get really bad gas mileage.
Do you have any idea how much pressure you are running under boost with the fmu? What disk do you have? I would highly recommend larger injectors, say 42's and a 80mm pro-m, FMU's are unrealiable and slow. You also need a larger fuel pump, the walbro 255lph for forced induction would work perfect.
Just trying to help, good luck...
Brad
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89'notch
331ci Scat Stroker, Stage II Holley heads, ported Holley Systemax Intake, 70mm Holley TB, 50lb Holley Fuel Injectors, 80mm Pro-m MAF, AFM B-3 cam, Vortech S-trim Supercharger, AFM Powerpipe, EEC-Tuner, TKO, Koni, Eibach, HPM, etc...
Beaten Daily..
http://lowkey.stangnet.com