Hi Chris....You need the unique code for the unit you are buying. This can be read by Rovacom.
The EMS code in your becm (2890)..see sheets sent to you, needs to be changed to the one relating to the new unit. Obviously needs to be done by someone with both the becm and Bosch Rovacom software modules. As your becm is unlocked, this is straightforward and does not need removal of the becm, and will take all of 15 minutes or so.
The new engine ecu cannot be coded to your old one (2890)..you have to code the becm to the new one..in a nutshell.