i know you all are convinced that it's coming from the rear seat area, but have any of u considered sticking the felt pads on the hatch bump stops? when i first bought my '03, i had an annoying rattle which i swore sounded like it was coming from inside. i couldn't find it; so, i started looking elsewhere. then, it seemed to be coming from outside; so, i put weather stripping on the back of the rear license plate. still, the rattle was there. it wasn't until someone on here mentioned the rear hatch bump stops and putting the felt stickers on them that the rattle went away. as for now, i'm rattle free (knock on wood).