I've been offered a servotronic hydro box and control module from a 1993 850i cheaply and thinking of retrofitting into my 91 850i. The servo steering in my E39 540i was a massive improvement over stock so I'm quite keen to give it a try. The internets suggest that the wiring harness for the control module will already exist located on the left hand side of the left hand foot well in the cabin and the hydro box should be a straight swap.
Anyone done this on an older car (E32, E34, E38, E39)? Any possible pitfalls (other than the possibility the wiring doesn't exist)?