Let me guess, Edelbrock.
Spacer helped a little on mine as did a fully circulating fuel system, but not a lot.
After a small short stop 10-20 min or so the carb goes really lean as referenced by my AF gauge, then clears up again after a 1/4 mile or so of running.
It's mostly heat coupled with the available fuel problem with Edelbrocks, as the fuel bowls are right in the body over the hot intake and not out on the ends like a Holley, and the newer fuels boil really easy.
The insulator may very well help, but I wouldn't expect the problem to completely disappear because of it.
The term heat soak could very well apply on an engine experiencing vapor lock, but that term also can apply to mechanical/electrical parts like starters.
The term vapor lock usually refers to only fuel.