fuel problems?

Have a 95 Lumina APV with 200,000kms. Lost power at highway speed, restarted, could only drive @40mph to nearest GM dealer. Problem was weak fuel pump. Got pump and filter replaced, now when starting idle is very rough, engine wants to stall unless feather accelerator to keep it running. After driving for a couple of minutes, returns to normal driving conditions. If shut engine off, will restart immediately and run normally. If shut off and let it sit for more than 15-20 minutes, same rough idle problem occurs. Any ideas where to look? Do not have any diagnostic equipment and only basic mechanical knowledge, so try keep it simple. Thanks

what engine does your van have?

3.1 litre. I suspect problem is 1 of 3 things...1) fuel pressure is too low - but why does it get better after engine runs a few minutes? 2) vacuum leak -- air being sucked in somewhere but problem goes away when things expand with the heat, 3) faulty fuel pump -- i doubt it. Where to start looking??

IT sounds like a fuel pressure issue to me. As it sets, the fuel pressure regulator bleeds off and makes it difficult to start.