I have the Chevy valve covers that you must drill your own holes so there are no baffles in the covers. Also running a pan-u-vac system on Rewarder headers with mufflers. We also put in the Moroso rubber gromets with just a slit in them. Durning the build Jim at Rewarder thought the pan-u-vac would work with mufflers. My engine builder looked into the collectors and said the bungs were flush and did not think that was good. Now we are getting oil on the covers and that's not good. We did a vac test and at 4-5K only saw about 5". The clear tubes only have a slight discoloration for about 1" at the breathers. Anyone have any ideas?