From what I understand, in the w126, more often than not the steering box is not the problem in loose steering. I would suspect that in Sixto's car which is a 91 the steering box should be fine. Shocks can cause poor handling when they start to wear that feels like a steering problem. There are many variables however, so a competant tech should check it out.
1995 E420 - retired
1986 420SEL - retired