I read alot on here about valve stem problems being very common. I have a 92 rs305tbi and it just started smoking at startup and when you rev it up quickly. The smoke is white......could it be a stuck ring or can valve stem seals smoke at start up and also at acceleration. My local shop told me that this year model had good valve stem rings? I just need some advice.....it runs great...almost as good as new with no overheating problems......is there an economical fix if it is a stuck ring.....HELP?????????????