I finally found the passenger side rattle that's been driving me crazy. I noticed the noise seemed less with someone in the passenger seat so I went under the seat with a flashlight. I was able to duplicate the sound by lightly banging around down there. There's a little black control box right in the middle of the seat. A bit of scrap rubber between the top of the box and the seat completely removed the sound! Even if it falls out or something I at least know where the noise is coming from now!
I'm also in the process of putting Gummi Pflege on the sunroof and door seals to get rid of the squeak. The first application didn't take care of it. If it doesn't work I'll have to try the Velcro pieces.
I had trouble articulating the passenger side problem when searching, so hopefully this will help others.