engine problems on 2000 Pontiac Grand Prix

when you start the engine it idles fine for 2 to 3 seconds then shuts off. if you rev the engine up and down at 3 to 4 thousand rpm you can keep it running but if you hold a steady throttle or let it idlr it dies. It dosent miss or smoke and i havent found any obvious vacum leaks and i have changed the maf sensor and it dident change anything.It is a supercharged 3800

It still sounds like a vacuum leak or air intake leak -- just maybe a not-so-obvious one. Could be fuel pressure issue, but not as likely.
I started the car and sprayed starting fluid around the intake and vacum lines while i was keeping it running and it didnt seem to rev up anymore. i dont really think it is fuel pressure because it revs good ans dont miss at all. i dnt have any tools to check fuel pressure though.
Revving good and not misfiring are not signs of proper fuel pump operation.

Flying blind really isn't going to work in testing your car. Unfortunately, you're going to need the assistance of a tech and diagnostic tools.
Fuel pump resistor There is way to bypass to make sure