About 2 days ago, i recently lost a lot of power out of my 91 3.0. The truck ran great before but now is completely slow. It started while driving down the road and the truck began to become slugish. All of a sudden the truck would regan its power and make its way on. The very next day the motor just doesnt want to get up and go anymore. Throughout this week i've replaced:

-spark plug wires
-fuel filter
-fuel pump
-spark plugs
-dist. cap
-rotor button
-TPS
-AFM
-air filter

The engine doesnt hesitate or anything now its just not as powerful as it was the other day. Just recently i began to see oil spilling out from somewhere on the top of the engine. I cant find the exact spot but i know its coming from around the top of the tranny. I am beginning to think it may be the lower intake? I have no leaks in any vacuum lines or air intake, but maybe the lower intake is causing this? The oil leaks like crazy, i know its not the valve covers because i just replaced the gaskets, but its coming from around that area, and runs down the motor, down the side of the head and then onto the tranny and then to the ground. The motor now also shakes like crazy at idle. Gears have become harder to engage, especially reverse and 3rd. I've been replacing everything i thought it could be. Only thing i believe now is the fuel injectors. But the oil leak just started so i am believing it is causing the engine to run poor. Anyone have any ideas of where it could be leaking from up near the valve covers, its coming from along the firewall somewhere and then dripping down the driver side of the tranny. Could the lower intake be leaking?