Crazy Rattle in Right Rear! Help!

[Doug1227]

Hey guys, I've been battling a horrible rattle in the right rear corner of the mustang for several months. I've put my hand on damn near every bolt underneath this thing trying to find it. I've had NTB and Goodyear put it on a lift and try to find it. I'm at a total loss. I need to know who I could take it to that can DEFINITELY figure out what it is. The car has the following mods:

Lowered on Sportlines
Koni Yellows at full soft
Stallion adjustable panhard bar with poly ends
Stock upper and lower control arms

I've jacked the car up and turned the wheel and don't hear anything.
I've had someone drive the car while I went head first into my trunk trying to find it. Don't believe it's coming from inside the car. Sounds like the right side, above the wheel...closer I get to the bumper the louder it is.
It's not the exhaust rattling, or a muffler bracket.
It's most noticeable over light bumps and is VERY easy to hear. It sounds like something is about to fall off the car! BUT I can't find anything loose.

I first noticed the sound on 3/25/13 which was after I had installed the panhard and the Koni's. I've taken the right rear Koni off and reinstalled it thinking I may have messed up something. I've reinstalled the springs several times. I've greased the panhard, but I haven't completely removed/reinstalled it yet. Might try that next. What I'm hearing sounds like something is crazy loose though... not just a creak or something.

WHO can I take this thing to who can definitely find it!??! At this point, I'm willing to even drop some reasonable coin just find out what the hell it is!