[robinasu]

Another question I have is if modules must have matching VINs. I read something where the active steering module might check the VIN, but not sure about that.

Also, just to be complete, I swapped in $541 into the vehicle order to see what would happen - same two "vehicle interface" errors. It's so weird the ACC option needs a different hydro block in LCI cars. The $544 option already has the brake function, so it has a pressure sensor in there. ISTA-P seems to look at more than the VO as it initializes. The car integration level must be determined somehow or is saved on a module(s). I'll poke around the new hydro unit/DSC ECU when it arrives.