I have a 1986 300E with an amazingly low 60K miles.
In the last 10K miles, the steering has slowly begun not returning to center. No matter the road, or speed, the car will go where ever the steering is pointing. It is difficult to drive on the interstate as you must constantly pay close attention the wheel to keep it straight.
I have rebuilt the steering box and adjusted it to specs.
Aligned front end.
Changed power steering fluid with MB synthetic fluid.
Replaced filter.
Replaced struts and strut bushings.
Replaced tires.

The power assist works great even at idle and sitting still. Everything feels smooth and easy when up on jacks.

I have been searching these forums and have found no similar problems. I would greatly appreciate any info to lead me in the right direction.
Thanks