I thought ceramic coating was the best for heat retention, resulting in a little more hp as well as holding-down temps. True???

Has anyone documented an ET reduction from headers alone ?

 

As far as ceramic vs. stainless, I logic says a coated metal header that is the same thickness as a stainless header would retain more heat, yes.

As far as ET reduction - yes, you'll definitely see a reduction. Others can post actual numbers.

 

I went stainless and coated: