valve cover bs from dealer

So i have been trying to chase this sound coming from the engine bay when my car is at idle or parked sounds like a gla gla sound. I replaced ccv last week cause thats wahtr they said was making sounds. But that didnt fix the problem the car runs better and the ccv were split but sound still there. So i take it back and nwo they are saying it could be a vaccum leak from the valve cover? And they wanted 1000 to do passanger side only along with the vacumm hoses. Tech claimed its a leak in the valve cover making those sounds but i have a hard time buying that cause the sound will go away it you hit gas a bit. Tech didnt run it on computer to check codes evern though there is no check engine lgiht but i just not buying it with him just looking at it in front of me and not taking it back for proper diagnostic. He said there is a new updated valve cover for the passanger side but i always thought it was the vent hoses not the cover. So if i can get some opionions from poeple here that would be great cause i dont think the dealer is really looking into it a whole lot. They claim valve cover is 400 for part alone that sounds outrangoes. Thank you johndade

there is a "gasket set C" which is about $400,

maybe the valve cover gasket is part of that set, but i cant see one gasket being $400