Replaced Differential Bushings
 

The Pettitt http://www.pettitracing.com/rx7/index_suspension.htm
urethane diff bushings are quiet "almost like stock" but are also stiffer.
I just installed them Tuesday and really like them.

As others have reported, breaking the 4 nuts on top of the diff is the difficult task. Since I am a small person and do not have super strength, I gave up on the normal methods after a while. I did not want to remove the drive shaft and PPF which would allow rotation of the diff for better access. My remedy was a 2 ton capacity wire cable winch, AKA a come-along.

I conneted the winch end to the side of the frame cross member and the doubled up cable end around my wratchet or box end wrench. The cable was routed as to pull straight as posible. It worked as I thought it would, easy.

Great tip! How long did it take to install them?

4 hours not counting the time to go buy the Come-Along and take the diff brace to a shop to change out the bushings. This includes jacking up the car, putting jack stands under it, and removing the rear wheels, and reversing this.