[CarPsyco84]

To answer your initial question, a .100" restrictor should work, but I would personally run it off the head, thats where Mitsubishi put it for their turbos, I would also see if that restrictor cup is in the inlet, cause if thats there, you should not need a restrictor at all. Even better, someone could measure what size hole is in that lil cup then we will know what size should be used in the event that is missing from a Mitsu turbo in the future.