Having a bit of a handling problem with my Saph. The steering feels very imprecise at motorway speeds, the car wanders a lot side to side, and feels quite unstable - you can really feel the tramlines in the outside lane. It makes it quite horrible to drive at anything over 60 ish.

The rack was leaking a week ago, I thought that was causing it, so put a new rack on, and tracking done and its still the same. The rubber donut in the steering joint looked fine when I checked, and the rest of the suspension has been done fairly recently (new arms, polybushes, tracking, etc). I've tried different wheels, with different pressures. No difference.
What can I try next?