I drive an 03 GMC Sierra 1500 with the 4.8liter and automatic tranny. My problem is when I drive it for say 20-30 minutes straight(generally when I drive from my town to another town) and then let it sit for a couple hours, when I go to start it it will stall out and the starter kicks over real fast. When I try and start it the second time, 50% of the time it will stall out again. The other 50% of the time it will start, bog/stumble/sputter, and then it will be fine. If it doesn't start the second time it always starts the 3rd time and I won't have another problem with it. I have been told it is either the fuel pressure regulator or the fuel pump. I replaced the fuel pressure regulator and a week later it was having the same issue. I did seem to gain some throttle response after swapping fuel pressure regulators but that was all I noticed. I changed it with a Borg Warner regulator from O'reilly Auto Parts. As far as the fuel pump being the culprit, it doesn't make the notorious whine that these pumps tend to make when they are going out and I have been experiencing this problem for several months now so I think if the pump was on its last leg it would have kicked the bucket by now.

The truck doesn't have any other problems besides this one and I usually don't experience this problem unless I've specifically driven it for about 20-30 minutes and then parked it for an hour or 2. Even more peculiar is when I drive it back from out of town which is a 30 minute drive, and park it over night, it fires right up in the morning without a problem. Any guidance would truely be appreciated.