escossie - do you mean how does coating raise the EGT's? If so, a ceramic coated manifold will not allow heat to be radiated out of it. The heat and energy therefore stays in the exhaust gas, and it does not drop in temperature.

I see what you saying about radiant heat but that is only surface temp of manifold not gas temp ,as the main aim of whatching egt is to monitor head/cylinder temp so you dont destroy your pistons or head the manifold temp is after this point so now only protecting your turbo.............so my piont being that depending on sensor position you may read a higher temp with a ceramic coated manifold i personally cant see there being that much difference with the gas velocity at full chat but even if there is a differance what is in danger as even with the manifold coated the gas temp from the head is the same, not being argumentative just trying to understand your point
cheers andy