There is a gray bar that is held down with three bolts under the rear passager seat. What is its purpose?

Side impact protection for the people in the back seat. It may also provide a little structural support as well.

Josh

Is it possable to use it for a three point harnse?

dude! that was my question!:D
anyhow, I was in the process of removing that yesterday when I realized it might be a safety feature and changed my mind. I'm still not convinced it should stay, though. I don't have rear seats, so rear passenger safety isn't a real
concern - but driver safety still is of course. It doesn't really look like it provides much structural rigigidity, who knows. I guess it stays for now.