I did post a while back in the truck section with some good info but still having issues.

1989 W250 360 pretty much a unmolested original truck. What would the cold weather affect on start up? Been struggling trying to figure out what causes it to run sorta rough spit and pops back through the throttle body and speed up and slow down at idle. I put it in the shop at 65 degrees and it runs perfect, put it outside in the 20 degree weather for a couple hrs. and runs like crap again. Sick of throwing parts at it.

New map sensor, throttle positioning sensor, ignition temp sensor,02 sensor,hall effect pickup in the distributer, different ecm. Hot air setup from the exhaust manifold appears to be working. Also took the idle speed motor off and it still speeds up and slows down, back on there now. I checked the codes and it only shows the battery disconnected code. I plugged the line to the vacuum booster with no change. Timing was spot on. What am I missing here? I am at a loss

moisture inside the dist. cap?

The ignition temp sensor? Would that be the 2 wire coolant sensor then?

Yes

strickly WAG ing, when you take it out from the warm shop does it act up immediate or does it take several hours of sitting shut down like you mentioned? I'm wondering if a coolant heater in a rad hose bringing the coolant temp up if it would still not be right when sitting outside which would point me toward A/F mixture. I'm just bored.

Fuel filter or pump flow issue maybe?

does it miss or backfire or just the idle hunting around? Idle surging like that can be a very lean condition and then the IAC starts to try to chase it around and it gets even worse

It takes a couple hrs then back to running like crap.

It pops back though the thottle body once in a while along with surging idle.