The car just feel unstable in the rear. This is most evident if you are accelerating in a corner and the let off the gas. The car dives towards the inside of the curve. Not so much as to be unsafe, but enough to be obvious and annoying.
Thanks for the ideas. It will be a week or so before I get to it, but I will lift the car and check the rear control arms for left-right flex. I am guessing that a valid check is to lift the tires a couple inches off the floor and crowbar under the tire in attempt to wiggle in and out at bottom.