[pampadori]

the spacers do keep the manifolds and throttle bodies cool since the plastic is such a poor thermal conductor. I can come home from an hour long drive and rest my hands on them without any discomfort. You can't rest your hand on them without the spacers unless you want some nasty burns.
With carburetors they prevent vapor locks (carbs have a bowl full of fuel that turns from liquid to vapor much quicker if its heated). I guess it can happen with efi too but there isn't a bowl of fuel sitting there so less of a problem.

If my memory serves me correctly - i ended up using a spacer kit from parts claissics (Can't type the actual name so you'll have to decipher it)