Good luck!
I'm hoping to do a little more troubleshooting myself this weekend. I'm really hoping it's not the springplate bushings rotating in the carrier. I used the Elephant Racing kit because I wanted the highest quality and they sure do seem like the real deal - not sure how that install could have gone wrong since it's a pretty straightfoward project. I'll update if I make any progress.

I have exactly the same noise coming from the right rear after having the plate rubbers replaced. Already replaced the swaybar rubbers since, but no difference. The spring plate rubbers were not glued into place. I think this is the problem as the sound is louder when cold and wet outside, and disappears after driving 15 minutes.