02 ls v8 hard to start when warm

i have a 02 ls v-8 ,car runs great,but i have a strange problem i got this car back in july 08,it had the org.fuel filter on it i replaced it,still hard to start when warm,i took it to the ford dealer to have it looked at. they said that the sox in the gas tank was pretty nasty they said it probally made the fuel pump weak,so replaced that same problem they found a tsb to reprogam the computer did that same thing while it was there i had them replace the valvecover gaskets they were starting to leak i also put in new plugs,they also said the tsb said to also replace iac motor same thing just hard to start when warm they have checked fuel presures , all sensors,coils,cant find anything, i have no check engine light on .any help would be great i have spent about a 1500.00 so far i love to get it fixed but ford cant tell me what to do HELP PLEASE i love the car

Have they checked the fuel pressure when warm, both KOEO and KOER? If the pressures are off and you have a new fuel pump, then you might have a fuel rail pressure sensor (FPS) that is not reading correctly. The FPS tells the PCM how to modulate the voltage to the fuel pump to maintain desired fuel pressure.

If the KOEO fuel pressure starts out good but quickly drops, that would imply that there is a fuel injector that is not closing completely or a leak in the fuel system.

-Rod

i called them this morning about that they said they checked presures both cold and warm and they were ok,thanks for the info.