Eliminated a few issues from old posts so this is narrowed down version.

Cold starts normally but lopes and misses. Occasionally throws a Big cloud of smoke and sounds like it's hitting on 3 or 4 cylinders for 10-15 seconds.
When warm, it idles perfectly, no miss and runs great.

What should I check for a rich cold start and run.
Probably takes 10 minutes, maybe 20min to run normally.

1992 straight 6, automatic.
new distributor, new computer, new ig module, new fuel pressure regulator.

I did see some sort of electrical 2 wire sensor in the coolant near the thermostat... manual is all but useless for testing sensors.

Thanks again

 

Get a spark tester and see if all cylinders are firing on startup. A barbaric way to do this would be to just pull plug wires one by one and see if it runs different.

You could have an issue with old injectors not firing properly that is amplifies when cold.

 

Finally found my plug wire insulated pliers so will try that today.
It's fuel injected but sounds like the choke is full on when it freaks out.
for a few seconds, like 10 - 20 seconds.
Always run non alcohol gas with something like sea foam, or stabilizer.
The slight miss when cold has been there for a while (1,000 miles) but this 'full choke failure' has happened 3 or 4 times out of 10 in the last week.

Will pull wires and report back.
Thanks again for that thought.
Very dangerous but seems predictable at this point.
Annoying to let it idle to warm up as it smells rich, misses slightly so I'll run it around the field and see if it falls on it's face before I hit the road.

Do these have a cold start injector, or enrichment circuit?
or just the 6 cylinder injectors.?

Check engine lite isn't on and no codes to be found.
Both tanks are full but no difference switching tanks that I can tell.

 

Check and clean your throttle position sensor. As for your 2 wired sensor, it might be your coolant temp. sensor. I don't think it would have anything to do with your truck running rich.