Brian Good-Wins's notes on Ceramic Coating. Frankly, it is usually only the mild steel headers that are ceramic coated and I had always suspected that the main reason was to slow down the inevitable rust that a mild steel header will suffer over time.

Since this manifold is already made in ALL STAINLESS STEEL, it does not need ceramic coating for rust prevention. That left the pure question of whether or not we could really find additional torque with the ceramic coating to justify the costs.

After lots of testing the answer turned out to be YES, at the points on the curve where our plain stainless header gets 12hp this coated version is consistently two points stronger, with peak hp up yet another 2 more to 160 hp at the wheels compared with 158 at the wheels for regular stainless version of this header (new dyno graph below), and a consistent 3+ foot pounds of torque from mid range to redline over the regular stainless version of this header.