[jararak]

there is official retrofit kit for e90 for mulf2 84640441949  - it contains fiber optic, P&P ocnnector for optic/electricity for mulf, microphone harmness and microphone itselve, same with BT antenna and harmness for it. i've already use it for e70, e90 and e60. costs just 110euro (very shaky price, once i buy it for 98euro, other day for 107 next time again 102e)

in case you want to install it with combox, you will need different connector 61136913644 and 61136913626

e90 - its perfect place on glovebox, there is also mounting plate possible to order, but in case there is cupholders, there is really big issues to fit it there.
in e60, i fit it to CDchanger location, but done only mulf2svx which is maybe 10cm shorder than combox, but it should work maybe if you cut a littlebit from combox