Rattle noise - R-Rear above wheel

I have 99 Boxter which is making a lot of rattle noise when I hit a bump on the road right around or above the right rear wheel. I've check the rear trunk board under the pad, the engine cover if loose and the top if any screws are loose, but they are all pretty tight. It is bothering me a lot. Left side is perfectly fine. Anyone has the same problem? Please share. Thanks