Not sure I understand your question, but, on a basically stock engine, you would never use a Motec or an Autronic...I couldn't see the benefit vs the return. The Unichip would be the way to go in that case. Piggybacks can only work within the confines of their own programming and how that integrates with the confines and limitations of the stock ECU. So, you can fine tune to a point that the Stock ECU will allow, but not beyond those parameters, as the stock ECU will keep compensating and adjusting accordingly.
You would never use the Unichip in conjunction with either the Motec or Autronic, they can do all that is needed as stand alones themselves...And I would expect that you would use them only with either FI applications, or a major NA rebuild...
Hope that helps a little...
Ryan