I've used RustOleum high temp paint for years on mufflers. If it cured a couple of days it worked great. My recent Spitfire project was to get a flat black muffler, but when I pulled the can off the shelf it was almost empty. So I bought a new can. Same label, same instructions, same contents list. It didn't even pretend to be fuel proof. First flight resulted in black spots on the airplane and a soon to be shiny aluminum muffler. Every bit of fuel that hit it took off some black.

I really wouldn't bet on any new paint working like it used to.