Squeaking, Popping Rear Suspension 01 Cobra

Anyone have any experience with a squeaking, clunking pop in an IRS Cobra? I left the car with the wife while on deployment. She had Ford put new brakes on it and then it sat for the next 3 months until my return. Now, I hear a serious clunk under low power / transitional power. I don't drive the car hard and never have. It almost sounds like there's a loose component. I pulled the rear brakes off and rechecked everything for fitment and security, everything was fine. I checked the 8 bolts holding the rear section of the subframe to the suspension and they were loose it seemed. I tightened them down with an air ratchet and it seemed slightly better for a bit. I checked them again last week and they're tight as a drum, but the pop is still there. I can even induce the pop simply by pushing down on the car with my weight and allowing it to rebound. The bushings all seem to squeak, as well. I've been reading and searching for other people with this problem. So far, I've seen a lot of stuff about IRSs being inherently sloppy, but this seems different since I can cause it to occur without even driving the car. One thing that I'm considering is the 14mm bolt replacement. Does that one seem to make sense to anyone else? Hey, I'm getting desperate here. My beautiful car's suspension sounds like a 1982 Dodge Caravan with 470,000 miles on it.

OK, I can understand why failure of those components would cause the symptoms I'm experiencing. But, if these components are soft and prone to failure, I don't think I'd like to replace them with the identical pieces. Does anyone make a heavy duty / poly version of these pieces? I didn't see any pix of the pieces or where they are on the car. I suspect they're kind of bears to get at, but curious to know if someone else is familiar with their location and/or has a picture I can refer to to ensure I'm heading in the right direction. Anyone?

Fixed it!!

I replaced the differential bushings with urethane... no change (they were hardly worn @ 60K). I put a '03 #4 brace... no change. I mean, both of these changes made a dramatic improvement in the handling and launch, but still the squeaking and popping was still there. After checking every single bolt with a stethoscope, I found that the upper nut on the right rear link from the sway bar to the lower A-arm was loose. I tightened it with a pneumatic wrench, hit all 3 others just to make sure, and took her for a test drive... PROBLEM SOLVED. Squeaking, popping and snapping gone! Check yours if you have this problem. It's a quick, easy, cheap fix.