I have an "interesting" rattle in my recently purchased 05 Shinka which sounds like it's coming from the rear passengers side seat above the wheel well.

The sound is only noticeable at high speeds on the freeway and sounds like a loose wire tapping against a panel.

I checked the seat belt and it isn't coming from there, nor is it coming from the window.

I think it would make the most sense to remove the rear passenger seat and surrounding panels but I have no idea where to start. The last thing I want to do is damage these panels.

I am wondering where to start disassembly. If anyone has instructions, I would appreciate it if you could send them my way.

I found rattle that are casued by the "clip A" on "rear package side/center trim" on my 8, not sure if its what caused the rattle that you have. Check out this thread which shows you how to remove the "rear package trim" http://www.rx8club.com/showthread.php?t=9991.html

Oke, I've had a rattle over there as well.

First thing you should do is drive with a passenger on the rear seat who can locate the problem. The interior acoustics plays funny tricks on you. In my car, the sound came from the other side than where I heard it!

Once you located the side, remove the seat, and the side trims.

I did numerous things:

There's a bolt in the corner of the rear window (you have to remove the airbag cover to get to it, the 'airbag' clip is removable to reveal a bolt) tighten that bolt (not too tight!)

Dampen all the wires running behind the side trim just in case.

Remove the rear deck panel (takes some effort, and to reinstall it you have to remove the metal clips first from the metal and place them onto the plastic shelf part) and dampen the big clip, and all the things that could rattle. Place some damping under the middle shelf as well (I suspect that was the problem in my case, but I'm not entirely sure)

It will take an hour at least, so keep that in mind.

Excuse me for my bad English lol :D