...but if you are satisfied so far and it is already working with the original motor... the only thing left to do is: adjust the steps/mm for the E-axis (on the printer), and you're through. Or did I got something wrong?
Send the following two commands to the printer, and that's it.
M92 E738
M500
The default value for the UM2+ is 369, you have to double it.
You can use (e.g.) Pronterface, or write the lines to a *.gcode file (with a text editor) and "print" it.
Keep in mind: The value is stored in EEPROM, you have to repeat this step after a "Factory Reset".
I will try this w