i believe this is the module:
"Part 65129289971 (Control unit with Active Sound Design)"
http://realoem.com/bmw/showparts.do?...=65&fg=25&hl=7
seems it's not that expensive, i've already found price for it at around 200$ in US.
It seems it's some kind of module or amplifier placed on the left side of the trunk, i've searched on the coding forums and there's a coding option for it. Would it be simple to install or it has to be tweaked by someone?
Anyone knows where could i find more information on it? or is anyone willing to look further into this?