dude If I had a nickel for everytime I found a new dash rattle.....
...I'd have a crapload of nickels. I keep telling myself I'm going to rip open the dash one day and find out where it is,but I don't :P
I've got a particularly nasty one that buzzes when I stomp on it. From about 3000rpms+ in 1st and 2nd it does it but goes away after that.
ugh.
Good luck in locating the problem.