Retrofit self leveling suspension

[ZetaTre]

I'm learning if and how the self leveling suspensions can be retrofitted in an E70 X5.

I found this topic: http://www.xoutpost.com/bmw-sav-foru...nt-x5-e70.html and it looks like the airbags simply replace the springs, so that looks fairly easy

Anyone knows where the pneumatic module is located (maybe take a picture) and where the control module is located? I'm trying to figure out if all cars are prewired or not, which would substantially reduce the work required.

Thanks!