Mfabsr20

I am having an issue with my sr. I installed a z32 maf, 750cc injectors, rs enthalpy rom tune, and an isis fuel pressure regulator. When I start the car initially to warm up, everything is fine. When I disconnect the vacuum line from the isis regulator, the car actually seems to idle better. When I plug the vacuum line back into the regulator, at the appropriate fuel pressure, the car get really lopey, uneven, then dies out. Could the problem be with a faulty regulator, or could I have vacuum leak somewhere like the wastegate etc. In the process of trying to diagnose my problems I redid all of my vacuum lines. Again on initial start up everything was cool, until I tried to adjust fuel pressure. Any help would be appreciated. Thank you