Supposedly both.

I didn't see any data on PWR page. It needs to be tested on the dyno with hp tuners. A lot of money for snake oil.

Did you email either of them about data?

I did,They said they are waiting on Tangable data from there testing partners but have seen a 10-15 degree difference on all GM cars.
Sounds good but I still need to see hard Data, preferably from a third party. It not trying to be a negative nelly but for that kind of money it needs to be backed up..
As far as the thermal plates and blanket they do keep the SP cooler at start up. I have the Fasterproms plates and the FI thermal blanket on mine and supercharger is much cooler to the touch than before.

Does anyone know the material of the spacers? Are they aluminum or a material that doesn't conduct heat as well? If they are aluminum, I don't see how they would help, considering they'd be conducting heat directly from the aluminum heads to the supercharger.

PVC

I don't know anyone that makes any for the LT4 but FI Interchillers spacers are more like a high temp phenolic and they do work.

Definitely not PVC; way too high temps for PVC.

OK, good to know - thanks.

I was being vague when I said pvc but it's definitely plastic didn't know we were being specific. BtW we have plastic all over the engine bay and attached to our engines.

OK. But saying "PVC" is not vague - it's a specific type of plastic. There's a lot of different types of plastics and polymers, so you can't say "PVC" when pretending to be general or vague. Some plastics handle heat much better than others.

So, it's some sort of high temperature rated polymeric material, and not aluminum. Got it.

I wasn't pretending anything, I work with pvc in my line of work so it comes out naturally for me. Why don't you just call the manufacturer next time.

I say it's probably a Nitrile Rubber Composite gasket/spacer. So many great composites out there that don't transfer heat. Superchargers/heads would seem to be a good application.

Looks like FI Interchillers now has spacer plates for the LT4.

https://fiinterchillers.com/shop/pro...spacer-plates/

I've ordered spacers and blanket