Alternate Seat Rocking Fix
I have come up with an alternate seat rocking fix that avoids seat removal and bushing replacement. The concept is to utilize a stop that prevents the seat from moving backward. Slight pressure is placed against the stop with the seat motor and the slop in the bushings is taken up and rocking is eliminated.
My particular fix is for shorter drivers that run with their seats pulled up such that the rear seat rail mounting bolt to the floor is visible. Also once the stop is installed you give up the ability to adjust the seat. I also run with my seat all the way down. I adjusted the seat to where I like it and measured and fabricated L pieces of steel that slips into both the seat rails (left and right) for a given seat. A hole is drilled in it and utilizes the rear seat rail mounting bolt.
In my case once the driver and passenger seats are set they don't need to be moved. I am the only one that drives my Z3. Everyone in my family is roughly the same height. I tell any new passengers not to try to adjust the seat. Also if I ever have to take my care in for service I will place a big sign in the car to not to try to move the seat backward or damage could occur (motor). I have not decided if I will later remove the seats and install aftermarket bushings (for latter resale value).
For taller drivers I have also come up with another "stop" concept type fix. I have not tried this one. Possibly a piece of cable with hooks on it could be used as a stop. The one end of the cable would hook to the front of the rail that attaches to the floor and the other end would hook to the rear inner rail that moves with the seat. The cable would have to be ajusted to provide the desired seat position. The cable would ride inside the rail.
I have a thick skin. Let me know if there are problems with my fix.