Doug's Headers Hi Temp Black Coating Question

Looking to get a set of Doug's D453B headers for by 67 Barracuda. Anyone have any experience with these headers, and in particular the ones with hi-temp black coating. I have two questions:

1. Does the hi temp black coated headers reduce heat in the engine boy (like ceramic coating headers).
2. Are the hi temp black coated headers hard wearing, does this coating burn / flake off?
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We have had them on our '66 a little over 2 years, it seems to wear better than I would have thought, but it does NOTHING to reduce the under hood temps.