I have a 90 f250 with the 5.8 351. I have a proble of a rough idle and or stall when it gets warm. It has a new iacv and new wires and plugs and cap. Any ideas as to why it would do that. It's a old farm truck with 84 thousand miles on it. Any vacume lines I should check. Any help would be greatly appreciated. Thanks.

 

Might you have water or other contaminants in the fuel?
Eric

 

Those engines had more vacuum controlled components than you could shake a stick at.
Try isolating them except for the fuel pressure regulator. The tomato soup can often developed a vacuum leak, don't forget to plug that hose and see if any change.
The coolant sensor allows a richer mixture when cold , is it working properly when warm?
If you can , might be a good idea to get hold of a fuel pressure gauge and check the pressure. You could have a fuel pump getting tired.