I'm in the process of swapping over to an LS6 PCV system and when i pulled the knock sensors one of them has oil in it. I havent pulled the valley cover off yet but my question is is the oil from the valley cover gasket leaking? Also i take it i should be on the safe side and replace the knock sensors while im in there?

 

You don't have to replace them if they are in good shape. Usually the front one is rusted and needs replacing. Just make sure you seal the grommets with silicone, This will keep water from getting in. Oil could just be from your intake.