Im sure its way too late but for the archives
Audis before CAN BUS can be wired without any by pass relays as bulb fail monitors are passive.
After CANBUS you need to use a seven way by pass device (basicaly seven relays with intelligence to act on various voltages at the rear lamps) . You will find that suppliers of these devices recommend them for all modern cars but the rule for us electricians is the CANBUS one plus Italian, you can check the Witter tow bars site and if the wiring kit is £39 then you know that includes a 7 way device
Barry
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