What Is Wrong

For starters do a cross check with a tape measure. Hook the tape measure on the lower ball joint and measure to the holes in the rear sub frame just in front of the rear axle. Should be within 1/4" otherwise may have to shift your sub frame as stated above to zero it out.

Have someone follow you the way it is right now and see if the car is slightly "Dog Tracking". This would be a sign that your K Member is not sitting in there square.

Also as you are driving let go of the steering wheel for a few seconds and see if the car pulls left or right on a level road. If it goes straight, then it leads back to K member being bolted in out of square.

It could be out of sqaure from a previous accident you dont know about too ?? K members can bend.