I have a 2.3 out of a 74 ford pinto.....has points distrib and motorcraft carb.  Idles great at start up.  push throttle down and sounds great all the way up to slamming throttle down to hit top end.  however, after letting off of throttle and rpms drop back down it idles like a diesel tractor and if you give it gas it just cuts out.  If you let it idle like that for 15-20 it cleans up and idles good again.....i have replaced every electronic part there is....rotor, cap, distrib, coil, coil wire, plugs, wires, etc. etc. i see no apparent vacuum leakes.  spray ether around intake and carb and there is no change.  Any other ideas?

Another possibility is that during the pedal floored event, the rpm is increased high enough to cause the hydraulic lifters to pump up and hold the valves slightly open.  When the rpm is reduced, the lifters bleed back down after a few seconds allowing the valves to fully close again.

The 74 2.3L had lubrication issues with the Lifters, and it will score that cam bad when the Chattering begins. Replace all the lifters, and make sure the rockers and cam lobes aren't toast already. This occurs on high mileage motors or ones that have neglected service oil change issues. Good luck!

Forgot to mention it has comp cam. Lobes all look fine

Have you taken a look at the internals like the cam, lifters & springs? There could very well be a mechanical issue causing your problem. Especially since like Pintosopher & Pinturbo75 have said they are known for some mechanical problems.

After careful analysis of the symptoms and consequences, I'm inclined to agree with Racer 99. The cam inspection was to verify condition of the followers and lifters. Yours are showing no wear, so unless a Oil pressure gauge reveals very erratic oil pressure that coincides with the dieseling and starving out, I doubt that the lifters, springs , or valves are the issue.

After thinking further about the symptoms, I wonder about the Headwork done to the engine. If all the other swaps had no effect, there is a chance that the mods to the head are causing Fuel dropout in the intake just ahead of the intake valves. Also the finish for the ports should be a lightly brushed texture on the intake side. No mirror finish on that side of the head (exhaust only). A vacuum reading should also show a wildly swinging gauge if the Fuel dropout is occurring. And wet plugs might be evident too. Just another possibility..