thanks to Jose's post and comments from all the people here, I finally managed to retrofit my 05/2011 e91 with a professional radio (05/2011) with bluetooth and USB.
I have everything actually working (bluetooth, voice commands, USB, aux), without any coding (though I already have the cable and programs).
However, I have some minor things that I would be interested to discuss/fix. I hope some of you may help
1. radio volume: well, at least at startup, the radio volume seems to be way too low with the new radio. I have to turn the volume knob quite a lot in order to reach a good volume level. Has it happened also to someone else? any idea on how to fix it?
2. voice commands works for english: is there a way to change it to another language (italian in my case)?
3. I have a very weird low volume gong after switching from the business to the professional radio. The sound is completely different than the two gong sounds in Jose's video in the first/second post. I kind of like it, as it is not annoying like the old one, though the volume is rather low. Any one experienced a different gong sound? Any idea on how to raise the volume?