Hard start after warm. no light on. Fuel pressure good. fuel filters replaced. I have to floor it to start then takes awhile to catch. acts like running out of gas. Then works again.

SOURCE: 1997 GMC K1500 4x4 5.7 ex.cab SFI injection system

I would check the fuel lines themselves and make sure there is no blockage. If not you might want to check your fuel injectors and see if they need to be replaced. also make sure you didnt install fuel filter backwards.

SOURCE: hard starting after sitting awhile

if before you start if you hold the gas pedal just a bit does it start faster if it does its our idle air control valve that defective (iac) let me now pierre

SOURCE: 98 gmc jimmy loses power to a stop

the fuel pump could actually be malfunctioning. and the reason that you are able to restart and drive again is because when you turn the key on it is allowing the fuel pump to pressureize your system. but while the fuel pump is continuasly running it is loosing the fuel pressure. this is common on the cheap fuel pumps. i am not sure about were you got the fuel pump from but in all of my experiances with this problem i find that the fuel pumps have been boughten at a napa store.
i hope this helps you out.
and you could attach a fuel pressure gauge on to the fuel rail and start the car and watch the pressure to see if it is droping.

SOURCE: 1995 safari van w stalls when giving it gas.

maybe your iac valve is not working? it takes place of a choke or temp sender to computer could be bad which controls t I.A.C. known as the idle control valve,do you have any codes?

SOURCE: my 99 gmc sonoma wil start and drive fine untill i

if no codes yet check and clean egr valve ,pcv valve,air filter and/ fuel pump and pressure regulator may b dropping under load