Attention: TDR Forum Junkies 
Doug,
Dad's had his on for well over a year now and has had not trouble of his Jet Hot coating. If I were you I'd get the manifold, take it out and make sure all the ports line up clearly everywhere, do any small port matching to ensure all your transitions are smooth, and then send it to get it coated. He has the Jet Hot 2000 inside and out, and it came out as a light gray. Even after blasts to 1700+ degrees it has not discolored a bit. I think the inside "flow coating" is beneficial because it smooths the inside surface and will help keep the heat out of the metal and in the exhaust gas itself. For what it's worth, I have seen other coatings peel off after time, but haven't seen anything bad out of the Jet Hot applications that I have seen.
John
Dad's had his on for well over a year now and has had not trouble of his Jet Hot coating. If I were you I'd get the manifold, take it out and make sure all the ports line up clearly everywhere, do any small port matching to ensure all your transitions are smooth, and then send it to get it coated. He has the Jet Hot 2000 inside and out, and it came out as a light gray. Even after blasts to 1700+ degrees it has not discolored a bit. I think the inside "flow coating" is beneficial because it smooths the inside surface and will help keep the heat out of the metal and in the exhaust gas itself. For what it's worth, I have seen other coatings peel off after time, but haven't seen anything bad out of the Jet Hot applications that I have seen.
John
