Ever figure it out?I haven't gone as far as removing the jack and styrofoam yet. That's next on my list to do. I did adjust my rear seats and put them into the lower position and it could have reduced the rattle somewhat. But it could have also been re-seating and re-tightening the spare wheel. I also find that when my family is in the car and the rear seats are occupied, I don't know the rattle as much. I'm not sure if it's just because there's more ambient sound in the cabin or whether the kids' presence affected the rattling (which would lead me to believe it could be the rear seats). I still don't have a definitive answer, unfortunately, but I'll update if I find it.