I replaced both the inner and outer gasket on the passenger side cover. Quite a pain as I couldn't remove the cover from the engine compartment because of a bind between the air conditioning tubing and the wire loom above the fuel injectors. I ended up sliding the old gaskets out from under the cover while it was still roughly in place and sliding the new gaskets in. After my experience with the passenger side I decided not to do the drivers side as it looked even more congested and it wasn't leaking anyway. If you decide to try it this way you'll want to make sure the gasket is not twisted in the bottom left corner or you'll develop a small leak and you'll have to do it all again. Ask me how I know......