Even so-called "high temp" powders can't hold up to exhaust temps. They might be good to 1200 degrees or so but exhaust temps frequently get much hotter, especially at the heads.
It's why most in the industry have gone to ceramic coatings.
I thought I remembered you saying powders couldn't hold up. I almost posted as much in another thread recently, but I kept my trap shut, because I couldn't remember. lol
