I've been running the sfmu with silver spring, largest disk and bleed valve to juice the injectors. As of late, since I installed the walbro 255hp and kept the accel inline, I would dump a shit load of fuel into my engine when I nail it from 1st. If I turn the bleed vavle too far out it would only pose a problem at 15psi, because then the needed fuel is bled back to the tank which causes a not so nice lean mix. So I went back to the dark spring, 2.72 disk and largest ring. I have the bleed valve slightly open. Car has been running good so far. I know some are able to lower fp at idle with silver springs and others with the dark springs. Don't ask me why cuz I can't figure it out myself. I know Terry (Star Turbo Eclipse) uses the silver spring and got the idle as low as 7psi, with the silver springs, I can get the idle to 25psi. However quite a few other guys are only able to get low idle fp with the dark spring. This is just an update for you guys who are stilling using the ancient vortech sfmu. It'll suffice unitl MS becomes available.