My rear wheels in 87 GXL doesn't sit straight. When I park the car one of the wheels(and only one) likes to sit at a slightly toe out angle. I also have AAS. What could be wrong. The car drives fine, doesn't shake or have unuaual vibrations.

 

Are we talking toe, where the front of the wheel is pointed outward/inward, or a camber condition where the tire lays in excessively at the top? Tire(s) wearing on the inside? If it's a toe condition, that can be adjusted by moving eccentric on the front of the subframe. Left and right should be adjusted to the same marks on the subframe.