It sounds like you have a vacuum/boost leak. I'm not sure why it "has to be the maf," especially considering you explicitly mentioned swapping in a known good unit to no avail. I would boost leak test the setup before assuming anything else. Also, did you check the injector insulators (at the head)...they do harden and leak (as mentioned). Finally, does your idle ever change; that is, at start-up, does it idle at a certain rpm, but as the car warms up the idle changes (for example, 1400 at start-up, 1100 when warm). Finally, did you set you base timing (ignition) properly before bull-sh*tting around with all that other work? If not, you might want to start there.