Well guys... Seems that everyone's perspective has some merit in this discussion, according to this article in Hot Rod , where they tested the coatings for performance gains.
Terrific read. Thanks for finding it! My take-away from it is that the coatings didn't do much to increase hp's on the dyno, but most definitely reduce under-hood temps in a significant way. See below: "Testing coated versus uncoated headers on an otherwise internally uncoated engine showed no statistically significant changes in overall torque and power output, although the engine was up a couple of numbers in the midrange. It could be that stainless steel headers are just less sensitive to thermal-barrier coatings than typical mild-steel headers. In any event, ambient temperatures with a heat gun in the vicinity of the headers did show a 200-degree-F temperature drop near the pipes at the pipe surface. Although the dyno numbers don’t reflect this drop, in a tight engine compartment not using cold-air induction but rather ingesting inlet air from inside a hot engine compartment, a reduction in exhaust-radiated heat could translate into a big power gain: On a normally aspirated engine, every 10-degree-F inlet air temperature decrease increases engine power by about 1 percent. Even if the air were only 50 degrees cooler by the time it got into the inlet tract, that’s a 5 percent improvement."
