The only known 'good' coatings are the baked-on ceramic 'Jet-Hot' process, and this is fairly expensive but coats both inside and out so there is maybe a 1% power increase from better gas flow- if the headers are the correct size to begin with. Jet-Hot is a copywrited brand and is not 'equivalent' to anything else. They have branches all over the country and deal mostly in mail order. Good luck shipping 180s.... As Dan said, spray paints don't last a week.
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