Sputters and stalls on short stops

Had a rebuilt 22RE 4cyl engine put in a 1995 4Runner. Ran great the first several months but now has a hard time running after a short stop within ~20 minutes or so. I.E. Ill make a trip to the store and when I try to start afterwards it will go up to appropriate, ~800 RPM, then just drop to zero and stall. If I give it gas while in neutral for a moment and keep it at ~1000 for ~10 or more seconds it wont stall but has a hard time accelerating in first until shifting to second. Also when my AC is on sometimes the RPMs fluctuate. Dont know enough myself to pinpoint the issue, if anyone has an idea what it might be please let me know, it would be greatly appreciated. Someone told me it may be a pressure regulator, any ideas?

 

I had a very similar issue on my '95 3.0 V6. Used to sputter and my volt meter would be going all over the place (indicating a potential electrical continuity issue).
I changed out my distributor cap and it made a world of difference.
In case, I also bought plug wires and a new air filter, but never ended up installing them