this info is just a word to the wise and not carved in stone so other opinions are well come
when engines run they have blow by compression and usually have a pvc and a hose going to the air cleaner system. if this system gets plugged up then that creates pressure in the engine and will sometimes blow gaskets or seals.
i looked in my manual and all i think i see is a little hose going from valve cover to the air cleaner. that hose might be plugged or when changing air filter systems it might be crimped.
when we do gaskets we use like a 600 grit honing stone to take off the shining surface and put slight scratches on the surface to better hold the gasket.