I fitted yesterday the HIDs that I bought s/h off here.
I had read a few online guides before hand to get an idea - the main thing I noted was the polarity. I read that the bulb holder should have the red wires 'inboard' - near the engine side, and both black wires on either side should be towards the wings....sounded simple enough.
My HIDs came minus instructions - but had been removed from a mk5 so should have been simple enough.
I fitted the pass side with red with inboard, and indeed had +12v at the +ive terminal into the ballast.
However on drivers side - red inboard gave me -12v at the red wire into the ballast. So I had to transpose the wires coming from the bulb holder to ensure the ballast got +ive into the red.
Wierd and just my findings, but it all works.!