Something to keep in mind with upgrades is that while the factory "locked" ECU is adaptive to a large degree, the adaptive fuel/spark maps it creates are lost when the ECU is disconnected from power i.e. the battery is disconnected. It will of course "re-learn" the current engine set up on re-connection, but that takes some time/miles.

The "unlocked" ECU gives you the option of merging the "learned" adaptive maps with the baseline map, thus creating a new baseline map stored in non-volatile memory. Adaptation to changing conditions still occurs, but referenced to the new baseline.

Steve
Late 2012 M3W