Iv dont absolutely nothing
Under peak torque you can feel my whole rear subframe/diff twist,i had the rear subframe out last week and theres evidence the bushes are frequently bottoming/rubbing on the stops,have thought about installing harder mounts but dont want the noise.
I guess the easy upgrade would be to make custom rubber mounts for the diff and subframe,and if thats not enough strengthen the subframe with welded or bolt on support.