Do you have a flange towbar or detachable? Also do you need the sensors to not work whilst towing or not pick up the towbar when not towing?
I have fitted fromt and rear oem sensors and im planning on fitting a westfalia detachable, these come with all required electrics but also needs coding apparently to allow the cut out when towing feature. I do know of another audi owner whos oem sensors dont sense his fitted flange towbar.
Its always difficult to tell with non genuine kits unfortunately.
Cheers