I have a 1991 chevy k2500 with the 350 tbi that is stock. When I start it up, if I dont give it any gas, it will stumble, shake a lot, and eventually it shuts off. If however I give it a few revs on startup, it will idle perfectly fine. Also, if I start it up and let it stumble for a bit but then turn the key off, when I start it back up it idles fine. I replaced the fuel pressure regulator in the throttle body, but that didnt fix it. I think it might be the fuel pump? I want to get yalls opinion before replacing that though. Anyone got any ideas? Thanks for your help