[s-cars] Rear Wheel Steer??

[tr0910 at softhome.net]

Every once in awhile I get a subtle surprise response from the chassis
during a lane change, where the car feels that it is doing the steering for
me.  Usually its related to cracks, ruts in the road etc.  I would blame the
tires, but it feels a little bit different to that.  Are there known
suspension bushings / linkages that need to be replaced in a 93 S4 with
140K?

Otherwise the car feels tight, so perhaps its just tires (Firestone Firehawk
SVX 16" std size with 15% tread left)

I plan on putting a HAP RSB on it, but I wonder if that will help??