Bad oil leak on 95 maxima..anyone ever ran into this problem?

I have replaced both valve cover gaskets,upper and lower oil pan
gasket,oil switch and still leaks badly when car is running.  After I go
on the highway and come home and open hood up there is oil on top of the
engine. There is puddles on top of the intake in the little valleys.
There is oil inbetween the rear of the front valve cover down where the
injectors are yet there is no oil running down from the valve cover.
There is no oil on the hood pad as well.  The timing cover looks dry...
I dont see any places up there where oil can come from?   Its a 95 se
with automatic trans.   Thanks:)Nel