i've never heard that, i thought blue was oil. i know that blue is oil. the cat was used, no chemicals to burn off, only carbon. i'm into the top end, camshafts are out, next gotta pull the head off, i think the valve guides might be gone as well as the valve seals. theres a lil bit of play between the guide and the stem, i'm not sure how much is too much. i know that the 351M in the ol' ranchero is FAR worse on gas than the 'tegra, so i need to get this done!