2003 Dodge Dakota Runs Rough and cuts out at 3000 RPM

My 2003 Dodge Dakota SLT with a 4.7 runs rough at idle, and it feels like the rev limiter kicks in at 3,000 since it loses power and sputters, though the engine stays on. Problem continues even after changing all the plugs and the air filter. Computer gives code PO 53 "Ignition Coil 3 or Ignition Coil C" so I put a new coil in cyclinder 3. Still the same.

Is it:

O2 sensor?
Catalytic Converter?
Fuel filter?
Other ideas?

Thanks....