Headers
My Opinion;
My non-coated TTIs went through 5>6 years as a 4-seasons DD, and a couple more summers besides, until the driver's side rusted thru in the merge. I took it down, brazed it up and it went another bunch of years. The P-side went a couple of summers further than the Driver's side, and then it too rusted thru in the merge. I fixed it. Around the 10th>13th year, IDK, I wasn't keeping track, they both started spitting. I couldn't feel any power loss, so I just let em spit. By that time the car was aging rapidly anyway.
Ok so it cost me a couple of hours each time fishing the headers outta there, and a couple of inches of rod; no big deal to me, certainly not worth the coating, to me. In my wildest dreams I never expected the same headers to go even 5 years never mind 15 and many more. To this day, the rest of the uncoated TTI headers look fine.
IIRC, TTI said the uncoated headers were nickel-plated and the rest was aluminized whatever that means.