WEll, on units with the timing chain, there is a rubber plug located there. This rubber plug can leak. When I replaced my valve cover gasket, it came with a new plug. The is a plug on both ends of the engine block. THe brand of gasket kit i bought was a Felpro, but I'm sure most kits come with new plugs. When you buy your kit, purchase a tube of RTV silicon, preferably the black kind, since it looks nicer. Put silicon on the edges of the plugs, around the corners, such that is oozes out around the joints a little. DO NOT put the silicone around the gasket. Put some of it right where the edges of the plug will meet up with the cover. This way, when it gets tightened down, it will seal any imperfections that might occur there. Wait at least 12 hours before driving the vehicle if you can. You do not need any silicone on the oil pan gasket.