[TimT]

the thermal barriersprevent some of the heat from combustion from transfering to the head/valve/piston whatever is coated. it is claimed that the higher exhaust gas temps increase exhaust velocity, which increases scavenging

I have info from a pretty good authority who asked Porsche about the coatings on the 3.6. Porsche said just the ports, not the heads or pistons, because it messes with the combustion temps.

which confuses things further, as many (all) F1 teams, nascar and even Porsche race teams use the coatings. Perhaps its because they tear the engines down frequently, and get to see the "real" picture of what is going on in the combustion chamber...and more closely monitor a/f ratios and EGTS than we all do

I had my headers done by jet-hot, I took surface temps before and after the application of the thermal barrier and it does work on headers