[Stubby79]

Does that include the engine wiring harness?

If everything matches - ECU to sensors - then you might want to check that you don't have any broken wires going to the relevant sensor(s), and that the sensor itself is OK. Are we sure the donor vehicle was working properly?

The other thing that comes to mind is that it's staying in lean-burn mode, meaning it isn't recognizing/reacting to throttle input. That would point to TPS or MAP sensor, depending on which sensors these engines run. Disconnecting the wide-band O2 probably forces it to stay out of lean burn.

Your idle fluctuating when you turn on a load might have nothing to do with it reacting to the input from the ELD...the ECU could very well be noticing the RPM drop from the load and reacting to that, instead. I would assume it would maintain a higher idle when you put an electrical load on, if it was reacting to the ELD like it should.

Ground wires are important, particularly to O2 and other sensors that operate on very low voltage changes...it's a common issue to miss attaching a ground wire during a swap...or for corrosion to crop up after time...always good to locate and clean/check all your ground connections for your particular engine, and to the chassis.

Oh, and check your charging voltage...like having bad grounds, if the system voltage is low, the sensors don't appreciate it, especially on older generation fuel-injected cars. It could all be related to the ELD. Fix what you know is wrong before you try fixing suspected issues.