I've had my S3 since the start of the year, and there' always been an annoying noise in it. When I corner hard, something is loose in the car, and rolls back and forwards from side to side. I've had 2 weeks off work recently, so decided to get to the bottom of it. I started by taking the rear seats up, to see if anything was under there, but couldn't find anything. I've went further and further, until I've got to this point... I was running out of places to look, so I let a mate drive the car while I lay in the back to try and pinpoint the noise. I decided it was either in the tailgate, or the back panel in front of the bumper. I pushed 2 small magnets down into 2 holes in the rear panel (the orange straws at either side of the back panel have the magnets stuck to the bottom of them) and took it for a spin. I must have instantly picked up the problem with them.... 3 nylon lock nuts! In that panel rolling about. They don't even belong on the car! Glad I go that sorted!