Could be wrong, but I think thats where the cockpit brace goes. It's the bar that goes behind the seats, I think the 94+ cars have it.
http://home.epix.net/~dppluta/thebrg...ckpitbrace.jpg

I tried to install my Double diagonal yesterday and wasn't able to complete it. Did you use the directions provided by the seller or did you find something more descriptive?