I'm thinking it's possible you may need to recalibrate the steering if fitting a unit that's been calibrated in a different car.
The impression I got is that the power steering units are calibrated as a unit and not to the car. I just wasn't sure if there was something else that needed doing when swapping over.
Others who have bought reconditioned exchange units seem to have been ok, so I don't think it would need doìng on a used part either?