OP I have done this retrofit on 4 cars now. With original headlights and ballast.
All 4 cars had flicker problems when you startet the engine after the install.
I then coded the car my self with the XENON option, and the flicker stopped on all 4 cars. The last one we made yesterday.
So yes, you need the car to be coded, or else the flicker wont stop.
I am aware that on some cars it works without coding, that is unexplainable, but on all the E90s i have worked on, they needed coding.