http://www.youtube.com/watch?v=li2vdGewp7w
Hopefully the video link works.
When only one person is in the car, almost no squeak. Add someone to the passenger seat and there's a little bit of squeaking. Put someone in the backseat and it's crazy.. Video is with three people in the car.
It can't be recreated by pushing up and down on the back of the car or at either corner.
When you take turns or curves left it's silent, and when you take turns or curves right it's pretty bad.
Car is a 2004 Mazda rx-8 shinka edition, six speed.
Any ideas?