I have yet to find a decent TCU retrofit thread where the cable is fully detail in what it connects to.

Most are US market cars that are prewired for telephone.

Should you be able to find the cable part numebr please post a full retrofit thread so we can see how the cable connects up.

In my estimation, the cable will run the whole lenght of the car, conecting to the mic and Eject box, and connect at X400/X322 in the luggage compartment to access the power, iBus and audio.

That white connector X400/X322 is not available to purchase for building your own loom.

This is all supposition.