I have a 86 chevy 1/2 ton 2WD with a 4.3 engine and a 4 barrel carb. The problem is at take off. The engine sputters and stalls when you press down on the throttle, but if you feather it lightly it will sputter and eventually take off and giver. At high speed if you take your foot off the throttle for any period of time and then press it down it will sputter and almost stall but eventually catch and run. I have cleaned the carb a few times with carb cleaner(the pour in the gas tank type and the spray in carb type),
Oh and I forgot to mention It runs decent when cold and at high idle, but as soon as it warms up it runs like I mentioned above.

Any help would be greatly appreciated

Iac motor????