Hey guys wanted to get your ideas on this. Got a 1991 150 with a 5.0 HO thats stalling on idol. It only does it when the check engine goes out.

Some background on the truck. Not the original motor. Came out with standard 5.0 had an truck that had been wrecked and swaped motor found out after not being able to get it to start it was an HO. Fairly new transmission. New tps and egr. Ran fine then started this out of nowhere. Don't remember the exact codes but it was egr related 336 I think. Will pull code this weekend

 

You could try pulling the IAC, clean it with throttle body cleaner and a pipe cleaner. Be gentle and don't manually move the plunger assembly. When you spray it hold it plunger down so you don't let the TB cleaner pool in the cavity and find it's way inside. Also test your components with a voltmeter.