I've got a B8.5 S4 Avant and I've had the rear seats up and down quite a bit for runs to the local tip recently. Those who don't have an Avant, basically the rear parcel shelf fully detaches as does the bar that runs across the back of the rear seats (that contains a sun visor). Now recently I've noticed a very annoying rattle/knock coming from the rear . It sounds like trim rather than anything else, so I've gone through the process of elimination; Kid seats, parcel shelf, visor bar out, seats down. No rattle. All out but seats up, rattle/knock. So I know it's not the kid seats, parcel shelf or the rear visor bar. It only happens when the seats are back up. They feel tight and there is no play when I pull on them, so the catches are locking in place ok I'd guess. The noise sounds like something rolling around or banging in the boot, like a loose piece of trim etc but there is nothing I can find. Almost certain it is from the seats. All I can think of is that the catches on one of the seats isn't closing fulling and knocking on the latch. Has anyone else had any similar issues or any idea what it could be. Really, really irritating.