Ignore the 543 code. It is commonly set when the engine is stalled on an OBD-I system. There is no way that a faulty fuel pump can cause this error code.
If there is no CEL, concentrate on the secondary ignition system (plugs and wires).
If you are concerned that fuel delivery might be the problem, connect a fuel pressure guage to the rail and test the pressure. It will then be obvious if you are in the right area.
Steve
