hey man, don't get hussy on me, I have NO idea who has or who hasn't. Whose to say that Ferrea knows what the Z32 valve seat is made of? I would sure hope so.... Anyway I don' want to make this a pissing contest Ash, I just figured I would give you some information that you may find important. Aftermarket valves w/ the OEM seats have lasted over 20,000 miles while others lived a shorter life of 4,000 miles.