As ant said, you need an emulator to map direct and only a hanfull of people in the uk have them and even less know what to do with them.

Sadly the ecu`s vary greatly with the american ones being mapped for 87 octane which makes them terrible for the uk 318is
even the german ones wont work as there mapped for 92-95 octane and make the engine scream with eratic idle.

As above.
You have to read the map, then upload the new map and then shut the doors and lock the car with the key.
then unlock the car with the key remote and the car will start.
a nightmare if you dont know as nick will confirm.

BHP losses

17.9% FWD
24.8% RWD

All taken as average.