I've got a knocking noise when taking tight (and bumpy) corners at speed (as you do wink ), it can be felt in the steering wheel. A friend had a bolt shear on the steering rack of his V6 so I'm a little concerned.
However, I think its the wishbones as I've got the "wandering" under heavy breaking, are the two problems linked???
Sounds like the wishbones. There's actually little rubber between the wishbone and the brackets holding the rubber bushings. As the rubber deteriorates the edges of the wishbone start to knock on these brackets under heavy load (cornering, braking). The bond between the rubber and the wishbone can also go, so that the wishbone pivots inside the rubber. This gives a squeaky creaking noise as you go over sleeping policemen and the like.
I replaced the wishbones about 15000km ago, and the squeaks are back... Perhaps I shouldn't have gone to that trackday on the Hockenheimring!
Just wondering, wasn't Superflex or some other company going to do polyurethane bushings for the 155? I seem to remember that they were looking for car-owner to test the bushings.