what does the coolant temp sensor say when its cold. Does then comp think its warm and isn't supplying ample fuel to start properly. I have seen bad coolant temp sensors cause start up problems before.
other thing to check would be tps, if the comp is seeing a WOT it will shut off fuel thinking its in flood mode.
• Check the Engine Coolant Temperature (ECT) sensor with the scan tool. Compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees greater or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit.
• Check the Throttle Position (TP) sensor. If a sticking throttle shaft or binding linkage causes a high TP sensor voltage (open throttle indication), the Control Module will not control the idle. While monitoring the TP sensor voltage, the scan tool should display less than 0.85 volt with the throttle closed.
borrowed from gm's SI