I've just bought a pioneer HU for my a4 b7 2005 and from what I can work out the standard unit uses a low power signal to turn the radio on so doesn't have a proper ignition live, I've tried a wiring harness adaptor but with no ignition live it doesn't work. Do I really need to buy a canbus adaptor as well? I was thinking easiest option is run a ignition live from somewhere else to the wiring harness and that should work fine. Is this the case? I don't want the battery going flat by wiring permanent live and forgetting to turn unit off. And help greatly appreciated.