The engine stalling when the truck is sitting idle for longer than 30 seconds.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve but always run a OBD2 fault code as well as the cleaning procedure. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

Engine stalls or RPM fluctuates at idle up and down or dies near idle.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve but always run a OBD2 fault code as well as the cleaning procedure. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

Check that the connector for the mass air flow sensor is properly connected. You will find this on the ducting from the air filter to the engine intake. failing that start looking for a hole in the vaccum system(rubber pipes around the top of the engine).

check the actual fuel line. Also is it fuel injection or carberator

put a OBD II code reader on it see if it has stored any codes if not replace the TPS sensor and the MAF sensor do the replacements at different times so you don't buy one or the other for nothing

this is your problem:

Here are the most common causes of surges, stalls at stops, low erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake

Check your fuel pump presure. Pump is in the tank. Also try and loosen the fuel cap, the tank vent may be stopped up.

have you ever had the injectors checked. if not try runing some fuel injection cleaners through it and see if that works

Sounds likes a Idle Air Control valve IAC problem.

i think you should change the fuelfilter.