Bounce test on rear shocks doesn't work too well on this car with all the rubber parts holding the shape of the suspension. You practically have to get the shock out to test it. But this is not likely the cause of your wander.

I had similar issues and started replacing all the links, etc.. and then got an alignment .... only to find out I had about 1 inch of toe-in!! This was definitely the largest contributor to rear steering and was causing inside edge balding on right rear tire... down to the metal.

Moral of this story: just check your rear toe using a string method and see where you're at BEFORE tackling all the suspension parts, bushings, shocks, etc..

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Cheers!
Scott McPhee

1987 300D