I looked through the DIY instructions for the E90 Homelink Retrofit Kit. In terms of wire count, I think everything but 1 wire is there with the retrofit harness. The only 1 wire missing with the retrofit harness is the earth wire which for cars already with the cable to the rear view, you can just swap it over to the new harness.
For cars without an existing 3 wires cable however, there will not be an existing earth wire available to swap over from. This sort of implies the need to follow the European instructions to ground the earth wire all the way through the A Pillar??? That will make the difficulty with this retrofit a lot higher.... I mean, how'd I be able to route the earth wire all the way to the bottom of the A Pillar without removing the headliner and the A Pillar liner? How can I even do that?
Another issue is, the DIY on e90post mentioned that the 61 12 0 434 330 retrofit harness have the branches A6 and A7 pre-cut?? (Wire count of 4 instead of 6). Can anyone who have bought the retrofit harness before comment on whether this is the case (A6 & A7 pre-cut, hence only leaving 4 wires instead of 6 on the harness). Thanks!