I think the hissing noise may be a common things with the catch cans. See if this helps:I installed a oil catch can a bit ago and now I have this noise like an air leak. If I pinch one of the tubes it stops so pretty sure its from the can but everything is tight and when you put my hand around trying to "plug" the leak and listen for a change I can't. So my question is does yalls do this also?
I recorded the noise but the file is too big...