I have been recently reworking my 92's suspension. She rides on some Dunlops fm901s that look like new...but have been on her for awhile. And she doesn't get driven much.
I did poly the bushings (both ends) of the trailing arms, replaced the original springs and shocks (front and rear) with IAP performance springs and Koni Reds, and installed a chassis stiffener. I didn't rebush anything in the front, but checked all for play. Got an alignment. And rebalanced and rotated. Still got a little shake..but I attribute it to tires sitting too long in one position. The chassis stiffener has nearly eliminated cowl shake, but its not as effective as it is on my 78. The S4s are just plain more flexible. But its much improved with the stiffener. The rear trailing arm bushings eliminate rear steer going into a corner. I found one front bushing bad, the rest were good. Of course, the poly will transmit more axle vibration...so if the diff needs service, you'll know it as the growl will transmit to the body.
I think you have a bad tire. Especially if the lower balls on the front are good. Got to be either that or a bent wheel.
Best Regards,
John M