Strange oil leak on 95 maxima Se..

Hello, Its an automatic and I have replaced both valve cover gaskets,the upper oil pan gasket,oil sending unit,lower oil pan gasket and still getting an oil leak when the car is running. After a trip on the highway at a higher speed I come off an exit and there is smoke everywhere. When I look on the intake manifold in the little gaps on top it is full of oil in there yet no oil underneath the hood. The injector area on the front (towards radiator) is full of oil and it seems like the oil comes from the injectors area?? Any ideas?? Thanks :)Nate