Valve cover warped -- solution
The best solution is to clean everything off real well --all the sealing surfaces with brake cleaner on shop towels. Then use black RTV on the head and valve cover gasket surfaces and put the two together. It won't leak again.
Infiniti doesn't use gaskets they use RTV everywher and they do not leak oil.
Lots of auto manufacturere asr using RTV's in lots of places now rather than gaskets.