***Resolved***
The problem was a bad aftermarket fuel pump (Airtex). I bought a Delco Fuel pump from RockAuto and installed it, and my problems were cured. Just another story that confirms that Airtex make a crap product. Just letting everyone know for future reference.
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I have a 1999 Grand Prix GTP. Old fuel pump kicked the bucket, and I was able to replace it without too much trouble. No issues prior to replacing the pump.
Now, the car runs fine, no issues with idle, cruise, or WOT. But it does have an issue starting up: I have to hold the key for several (5+) seconds.
The fuel pressure gauge reads a solid 50 PSI when the pump primes, but once the pump stops priming, the pressure almost immediately drops to zero. After starting the car, the fuel pressure goes back up to around 40PSI and stays solid there. No driveability issues.
I found that if I start the car while the pump is still priming, it starts right up. Seems pretty obvious the hard start issue is due to the drop in residual fuel pressure between the priming of the pump and starting the car. There are no obvious leaks in the fuel system.
So, did I get a bad fuel pump? I would imagine the FPR can cause this type of issue, but it was fine before the old pump died.
