Code PO304

1997 mercury tracer: code po304 Runs rough intermittenly and it is hard to start sometimes. Replaced egr componets, plugs and wires, checked compression ok until code appears. Replaced all vacume hoses. Replaced intake manifold gaskets and that took care of a tapping noise. Still have the same problem po304 Intermittenly. Sometimes the check engine light will clear it self. Put a new fuel pump and fuel regulator. Fuel psi now with key on 40 psi and started 32 psi. I would just junk this car but it is my my daughters car and she is in college. Would like to get this car through a couple more years.I do most of the work myself.