My 96 rs4 stag has had a problem since I have brought it , driving specifically between 85-115kph, I would estimate, I have a shuddering or 'pulsing' sensation coming from what I believe to be the rear axle of the car. Like additional torque is being applied to the rear driveshafts momentarily in an on/off fashion. I would say that it is not a reducing speed sensation, as in abs acting on the rear wheels for some even more bizarre reason, especially as it only happens at a light load throttle position and the sensation is destinctly coming from the rear end. Also it only seems to only happen when it's been running for a while or fully warmed up. Anybody got any suggestions or ideas as to what could be causing this to happen?