5.3 starts fine cold but trouble when hot

[Bryce]

I have a 1999 GMC sierra 5.3L step side I recently completely rebuilt the engine and it runs amazing and idles like a gem, the problem is when i start it cold it will start fine but when i run it for a bit and try to start it again when it is hot it will start but it sounds like it wants to stall out but wont, I thought it had something to do with the purge control valve but i checked all the wiring and and replaced the valve as well, If anyone knows or can help find the problem it would be greatly appreciated.

[davester]

maybe check fuel pressure when it's doing this?  maybe there's a problem with the fuel-pressure regulator and/or vacuum line to it?