I found this link with factory part numbers for TCU and ULF.
http://www.bimmerboard.com/members/p...artNumbers.pdf
Also googling around the other forums it seems fairly common that the earlier TCU audio quality gets bad over time.
In my 2005 4.8is which has BMW assist button I found TCU 88146946993-02 in the rear. Looks to be the original 1st gen.
I have found that resetting it by unplugging it for 5 mins will let it pair and audio works through all of the speakers for a while (day to weeks). Then the unit will glitch and audio only comes from front right speaker.
Even while working the audio has some static in it.
Has me wondering if replacing the unit with newer might help.
When I checked the unit I also found a bunch of the plugs not used. Can anyone confirm if these plugs should be used or if the one connected is in the right location??
I have also heard there is a mic upgrade but the static I hear is iPhone to car.