I have a 2002 '52' plate X5 4.4 and have recently upgraded the nav unit from MKIII to MKIV. I've also just ordered Rolf's interface unit, and have a couple of questions which I would be grateful for some answers to.

Firstly, with regard to accessing the i-Bus, I note that the 3-pin plug at the back of the CD unit is most commonly used. Whilst that is OK, I've noticed a few other unused similar 3-pin plugs on various wiring looms in the area of the CD & Nav units, are all these i-Bus connectors?

Secondly, when I upgraded the Nav unit from MKIII to MKIV, I lost the facility whereby a selected destination would have its "Distance" and "Arrival Time" automatically fed across to the Board Computer. Furthermore, when the Nav unit is actively guiding me to a destination, I can't even manually input a "Distance" into the Board Computer, to do this I have to turn guidance off, input the distance, and then turn guidance back on.

The Nav unit came from a German X3, and upon searching X5 World for an answer, it may be a simple case of recoding the unit by ticking the Navcoder "Show Arrival Time" box which is applicable to X5s, is this correct as it's both "Distance" and "Arrival Time" that are affected? If this is not the case, I have also learned that software downgrading and re-upgrading may fix the problem, but how (and with what) does one downgrade to an earlier software version?