While puttin in the new o2 sensors i noticed that they dont want to thread in there very easily... I have quite a bit of rust on my XJ and im just wondering if the threads on the exhaust might have some crap in them making it hard to get the ones to thread in there? I know they are supposed to get a good seal but this seem a little bit excessive... Any kind words for me?

 

Cleaning them up lightly with a small wire brush then applying anti-seize on the threads helps.