Alright got a 90 k5 with original 212,000 mile tbi 350 with center bolt valve covers. I started with originals and never leaked a drop of oil. Well when I went and put valve seals in I got the bright idea of putting gm performance chrome bowtie covers on since then they have been leaking. I tried fel-pro corks and rubbers and mr.gasket extra thick corks on the bowtie covers. never stopped leaking. I then went back to my stock covers. I used felpro rubber cork and then I even went to gm and bought the $12 a piece oe valve cover gaskets and that is what are currently on there now and they still leak oil. Do you guys have any remedys. This is gettin old and would like to know of any helpful hints you guys may have thanks!