'98 Cad. Catera, DTC P0300, P0303, P0304

1. Make and Model of your car - 1998 Cadillac Catera, 3.0L V6
2. Current odometer reading (approx) - 112000
3. Stick Shift or Automatic Transmission - Auto
4. Strange sounds or smells (if any) - smells hot, with an emission odor, burning oil
5. Fluid leaks (if any) - small regular coolant leak, occassional oil leak
6. Past repair history (if applicable) - Mechanic replaced the radiator and a valve at the firewall going to the heater core.

Car idles very rough most of the time, seems to get hot quickly. Has an emissions odor, smells like burning oil and has an occassional oil leak. Leaks a small amount of coolant regularly.

Seldom idles smooth, but when it does it seems to run okay and at normal temps.

I have also noticed that the oil pressure rises to maximum when the accelerator is pressed, drops back to normal when coasting or at "idle".

Today the Auto Zone tech checked it with an OBD II and it read P0300, P0303, P0304.

Previously another store had read it as a bad EGR valve.

Does this thing even have an EGR valve?
What else could cause the multiple symptoms listed above?

This thing is getting worse and I am getting desperate.

Would appreciate any help and advice you could give.