I had my cantrell headers and exhaust ceramic coated and the highly unscientific test is I noticed my trunk and engine bay temperatures seemed cooler than with the stock exhaust system.
It's too much of a PIA to install header, run without coating, measure temperature, then remove header, coat, reinstall and then measure temperature.
Much easier to find a stock NSX and measure temperatures against...maybe on the next get together here...
I think the cat's may run a little hotter now if the ceramic coating keeps hot exhaust temps in, then the catalytic converters will see more heat.
1991 Berlina Black, Tien flex suspension with edfc. Power slot rotors with RB pads, CT Engineering Header and Cat back Exhaust, CT Short Shifter. Volk GTF 18"-19". CT Supercharger next...
BATMANs: How'd the white coating hold up? I'm considering doing the same to my headers.