A bunch of LX engines prior to 02 had the exhaust manifold problem. It tends to crack in an area that is not easily seen, and it gets worse with age. Lexus replaced the ones that went bad during the warranty period. The replacements do not seem to have the problem. If you find a used one, be wary - it may have the same inherent weakness. Ordering the replacements should give you the updated parts - whether from Toyota or Lexus. If you know of a good mechanic, they can replace the manifolds. I just would not get a used part for fear of getting one of the faulty ones.