I have a ST4000 autopilot that does not track properly. This unit was already installed in the boat when I purchased it and has performed fine until recently. On an upwind heading with the pilot engaged, the boat wanders off course in all wind conditions. In a puff the boat will pull upwind sometimes as much as 10 degrees before the pilot is able to bring the boat back on course. By the time it responds, the wind eases back and the pilot now will over compensate in the other direction. I've tried adjusting the sensitivity selection to level 2, and also adjusted the rudder gain to no avail. This unit used to track right on course making small corrections as we sail along. I understand sailing down wind is harder on a pilot,and tracking is more erratic, but I,ve never had problems like this sailing up wind in light to moderate air with small waves. I would appreciate any help you be able to provide. Thanks, Howard Sherman S/V Escape