[jonnyk]

How does the FMU add fuel pressure? How does it know how much fuel pressure your rail regulator is holding?
I still think you guys are wrong on claiming that.
9 psi with a 12:1 FMU would put your fuel pressure at like 150. That is totally unbelievable to me.

It makes even less sense when you think about what an FMU really is. It is a boost responsive regulator. But, it runs AFTER the rail reguatlor. So if it's responding to 2 psi of boost at 12:1, it will attempt to hold 24 psi of fuel pressure in the rail. However, that is not restricting any fuel flow since the rail regulator holds closer to 40 and the remainder is just bled off. So the pressure coming out of the rail is 40 psi, the FMU is only attempting to hold 24 psi, therefore it's not a restriction in the picture and is NOT adding any more pressure to the system. Unless there is some sort of voodoo I am missing here....