Depends, chips vary very little. Most off the shelf chips will be fine for 99% of MFi users. Buying a second hand ECU with a "chip" in it would be the cheapest way of doing it. Then you can just swap the ECU's over and drive to a tuner and get them to set it up. It only takes 10 minutes to swap the ECU's over.

All an RST chip does is remove the boost cut. It will have an ignition curve written into it too. There is no "mapping" as such, just some tweaking with some screws to get the fueling as right as possible.