Insulating is one thing, but I can vouch for idle/driveability improvements with the cheap 1/2" 4 hole spacer. There are many reports of increased low end with the 4 hole.

When I put it on, I think the carb was getting a better signal and I was able to close the butterflies quite a bit. My engine has always had issues with idling as it's a big cam in a low compression engine. That's the reason I went with the mighty demon because it had the adjustable idle-eze. Adding the 4 hole really helped for both heat and carb function in my case.