automatic steering.

To elaborate above, jack up car and support on the front frame rails so the front wheels hang free. Turn on the engine and see if the ps box tends to turn the wheels on its own. If so, center the valve body by loosening the 2 bolts and sliding aft or rear per the manual.

If above is OK, I would first suspect the tires. I have had more pulling due to tires than anything else. They should be identical or at least the same tread pattern, same inflation, etc. Swap left to right and see if the direction of pull follows the tires.