The fuel pressure regulator (attached to drivers side of the fuel rail) controls how much fuel pressure there is. There is a vacuum line attached to it from the intake manifold. That is how it sees how much boost / vacuum there is so it can...
its because the vaccum signal is erratic now,now dead smooth like with stock cams..I work at Kayser Mitsubishi in wisconsin, and thats what the top mitsu tech told me,and he knows his shit.:thumb: