The subtlety may be in it being a 2017 US spec M3W and it could well have different mapping to the Euro3 M3Ws
In particular if it is setup to run on 93 octane that might reduce the tolerance in the closed loop trimming.
Unfortunately the locked ECU limits what you can read with ProTune but you can see the software version and any fault codes.
I would be tempted to fit the Stage 1 and see if the engine light comes on. If not you're good to go and if it does then the ECU can be removed quite ealsiy and sent back to MMC.
