Just wanted to share this -I just bought a 2007 Gti, generally good all round with a nice spec, standard issue, no mods, low milage BUT an annoying rattle from somewhere in the back (among some other bits and pieces that need attention). I removed EVERYTHING back there -seat bench, seat backs, tailgate trim, boot cill trim. I taped down all the cabling...still rattling. Rear door cards...nope, still rattling. Finally homed in on the reversing light/reflector sealed unit on the nearside of the tailgate and found the two lenses clipped together inside the unit weren't snug. Removed it from the tailgate, applied some silicone to the tongues protruding at the back, job done. So yeah, check for rattling lights! ......Loving this car....
