I ran one, a phenolic one from PFYC. I bought it because it was cheaper than the aluminum ones that were nitrous jet ready. I could really care less if it did what it claimed to do.
This phenolic one I bought was not nitrous jet ready, but a drill and a tap later it was.
It worked for me for many years, and I never ever had a leak.
I currently run an billet aluminum one, its not really there as a spacer, or a heat barrier, its there so I can bolt my LS1 throttle body to the back of my GenV.
~F~