Jack, I'm not sure why they tell you to use the rubber. The aluminum heads use a bronze guide and they do require a little more
oil than stock but almost every head I buy uses the teflon seal. You are right about the rubber, it doesn't last. I've only used the TFS heads once but I can't think of any reason why they would be different than everyone else. I've never tried a coating on the valves so I can't comment.
Don