Test fuel pressure after truck sits overnight or 6 hours
Or try this test after engine sits over night
Turn key on and count to 3, turn key off
Repeat this 2 more times
Then try to start engine
If it starts right up then you are losing fuel pressure over time.
The 40psi pressure should be no lower than 25psi after engine sits over night, and it will stay 25 or higher for a few MONTHS, not hours, days or weeks.......months
For safety reasons the fuel pump only runs for 2 seconds when key is turned on, that adds about 10psi of pressure.
Fuel pump won't run again until engine RPMs are above 400, so after it starts.
Turning key on and off 3 times would restore at least 30psi of fuel pressure to the system, if it had dropped to 0psi.
Also after engine is warmed up and idling, 700rpms, unplug the IAC Valve, RPMs should drop to 500 or engine may even stall either is good, no vacuum leak and IAC valve is working.
Long shot issue could be ECT(engine coolant temp) sensor, this tells computer when to run engine in "Choke mode", cold engines need extra fuel and higher idle to run.
Is the idle above 1,100rpm when started cold?
And then drops to about 700 after it is warmed up?
If so then ECT sensor is most likely fine.