I very well could be the heat shield. Mine rattled real bad so I took it off, no more rattle. The dealer installed a new cat under a recall (not because of rattles) and that heat sheild rattled also, so off with that one. If it is your heat sheild there is another heat sheild attached to the underside of your floor so I never felt heat coming through the carpet. I now have a MagnaFlow cat with no rattles.

Dennis

95 Sportage, gone but not forgotten.
98 Jeep TJ, 4" Zone springs with RC Long arms, Ford 8.8", 4.56 gears & Detroit locker rear, D30, 4.56 & Detroit Trutrack front.