I'm sure that my problem was what you're experiencing-it's really more of a clicking/ticking/plastic rubbing together sound rather than a rattle. One of our members had luck using silicone spray in the area of the seat-belt housing and his went away. Not mine! I tried lubing the trim without luck- Very annoying over your left ear as you drive.
Anyway, back to dealer for inlet hose recall and had them check this out as well. I really didn't hold out much hope-I figured oh well, someday it'll go away. But the dealer took care of it, first time. Here's the techs written description of what he did:
"Repositioned left rear quarter trim and lubed stops" Go to the dealer with that info and you'll hopefully be taken care of!
#16515 Graphite 6 sp.