Steering Issue

Put the car up on jackstands and repeat your test. If it still does it, you have problems with the rack.

How much slack are in the tie rod joints and universal & flex joint steering shaft couplers?

The universal and flex joint steering shaft couplers can be inspected with the car parked on the ground. With the engine off, have a helper rock the steering wheel back and forth while you inspect the universal and flex joint steering shaft couplers for excessive slack. You'll need a sharp eye and a strong light to do a good job.

Support the car on jackstands with the jackstands placed as close to the wheel as possible. With the steering locked, have a helper try to move each front wheel just like it would move if you turned the steering wheel. While they are rocking the wheels, you are under the car watching for slack in the tie rods.

Have the alignment checked to see if you have correct caster. More than stock is good, but too much difference can make for problems when you drive on an uneven road surface.