There's your problem. A low end suspension lift at a higher height without the parts to make it work.
First I would (if not done) loosen all the TB bolts and control arm bolts w/ tires on the ground. Shake around/jump on bumpers. Then torque to spec.
Just a guess here, but I am assuming this wasn't done and put a awful bind on the stock bushings.
If this doesn't help and since you said the rear. I would install a rear "axle side" track bar bracket to raise the roll axis. A track bar bracket will also center the axle better under the jeep.
You want to raise the track bar min 3" which most brackets will get you. Remove the frame side upper bracket and toss in the trash.
Teraflex makes a nice axle side bracket
3-3.5" of lift is a lot w/ just coils and shocks and why kits like that are cheap. Yea ... The quality is not as good as others, for the most part it's missing parts.
This should fix you up. Next I would be looking at a front track bar to center the front axle (again, at 3" it's going to be shifted 1/2" or so)
Then front lower control arms or AEV/Rancho drop brackets to bring caster closer to spec.
Good luck, any questions just ask.