1997 Dodge Neon No Power & Running Very Rough

The car runs so poorly that my son left it along the highway. I was able to drive it how by pumping the accelerator peddle all the way home. The OBD code stated a bad #1 oxygen sensor, which I replaced. I also replaced all of the spark plugs and wires since the spark plug tubes were partially filled with oil. I also replaced the valve cover gasket and and the four spark plug tube seals. Sometimes the car runs very well, but then it suddenly looses all power as if it has no fuel. I can pump the accelerator to keep it running and plan to check the fuel line pressure next. I also put in a bottle of heat to dissipate any potential water in the fuel tank. The timing belt looks very good and since the problems are intermittent I don't think it is the cause of the problem. I will test the fuel pressure next, but I am wonder if anyone has any other ideas?