I changed the fuel injector assembly from the stock CSFI to MFI about 30k miles ago. Now when I check fuel pressure, I read 55 lbs. Does anyone know what the correct spec for fuel pressure should be after you do the MFI upgrade on a 99my 5.7L Vortec? I am trying to track down a problem I believe to be engine related. It seems to buck & surge while I drive, almost like uneven cylinder firing. 99MY K1500 Suburban, 5.7L, 200k miles.