I have had the valve cover gaskets replaced at least 4 times. Both sides. Yet, still leaking. I think it is an engine pressure issue but my mechanic does not thinks so. I am not getting any errors, just smells like old chevy. Also, found oil past air mass sensor that appeared to be coming from heater hose.
If you have to keep replacing gaskets then it may be a pressure issue or your pcv system isn't working right. Check for a plugged hose or a bad valve. Actuall replace the pcv valve to make sure it 's good. Also if there are any filters that are breather type going to air cleaner replace those.I'm sending wo pics along check these for blockages. The onepipe connecting to the intake, see where it goes and check that area as well.