As to how to identify the CAN busses, infotainment CAN high is usually orange/lilac and CAN low is orange/brown. Comfort CAN high is orange/green with comfort CAN low bein orange/brown too. And powertrain CAN high is orange/black, low is ornage/brown again. The Bosch CAN was grey/red and grey/something if I recall correctly. Comfort and Infotainment are both 100kbps, powertrain is much faster (maybe it was 500kbps)./quote]
A few Audis have 2 engine ECUs (cars like the B7 RS4) and they have an additional high speed private CAN bus between the two engine ECUs.