Lane A and B check after start

Normal. I see this all the time. It could possibly be the way you do the lane check. It isn't exactly like the carb engine mag check.

Yup. There's always a bump. The bump tells you it's working. 😛

All ROTAX injection engines I saw have the same bump. I think it's because Lane A always has priority over the engine control, but Lane B doesn't.

I was told by Rotax that Lane B has a slightly Richer map than Lane A thus the slight bump in RPM's when B takes over.

All

Lane A is fitted with the bulk of the sensors and when both are running Lane A is the primary and only with all the sensors working can give you the ECO mode.  Lane B is mostly a map and always runs richer and can not run ECO mode on its own,  When doing MAG check it is normall to see a slightly higher RPM than on A.   The traditional MAG drop we see,  in the 912ULS for example, does not happen.  

Cheers