Umm, you may be interested in watching the Enginemaster video where Dulcich and Frieburger bash a set of headers on a dyno test engine with a hammer and back to back dyno pulls show no appreciative loss of power. If the theory of more flow equals more power was actually true, we’d all be running 2 1/4” headers on our small blocks. A .015” coating on the inside of a header is going to have a negligible effect on power.
