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Check out your Thermal vacuum tree and your Thermostat. The scanner may be blaming the part when in fact the part does not have vacuum until the engine reaches a certain temperature. A weak Thermostat will prevent the engine from changing the Ignition timing quickly.
Some of the engines used water temperature as part of the choke system. The Thermal vacuum tree would route the vacuum to different dashpots and solenoids. Not only would cold temperatures activate RPM increases, but separate dashpots would trip when the engine was hot enough to run without the choke stepup and drop the RPM down to curb idle.
This made choke settings hard to set because it took so long to cool down the block to make further adjustments. The Ignition advance was regulated by water temperature so the stalling and spitting back is from retarded timing.
Remember to use your scanner to wipe the memory clean after each repair. Look for the Vacuum routing label under the hood to make sure the hoses are correct.
I'm assuming its carburated???? is so, check that the choke is engaging and if possible, try cleaning the idle circuit in the carburator....these things are tricky.....also look for old cracked vaccum lines as the older trucks (mine included) are VERY sensitive to vaccum leaks.
most likely the air-by pass is dirty/sticking, while idling tap on the valve and listen for changes in noise, if changing, remove and clean with CHOKE spray and a small brush, if no change, replace the valve......prior to repairs get a HOSE and use it to hear where the noise is coming from...possible vac leak???....hope this helps...GL