I too, wanted to say lean. Didn't want to get laughed at. One of the biggest clues was your header coatings. The guys said coatings last unless there was something improper done, such as breaking in a new engine and letting it run to hot that the coating would not fail. This would be the result of running lean. You would have very high exhaust temps. This is most likely what caused your header coating to fail, also. Good luck, Stu.