I'm running a sniper on a ld4b intake with a 1 inch phenolic spacer. It's worked really well.
The phenolic spacer also acts as an insulator.
Why would you need an insulator? It's a return system.
Insulate the ECU in the sniper from heat transfer.
It isn't needed for fuel control since the fuel is at 60 psi inside the Sniper. Gas doesn't boil at 60 psi so vapor locking is not an issue. There might be a small performance gain by having the throttle body cooler but most likely isn't isn't noticeable. Keeping the ECU cooler might be a good idea in the long run since heat will shorten the life of the electrical components.
