The play that I and others have in the rack seems to be only in the LH side (on RH drive cars) and is apparent when you pull vertically on the steering arm. I think the play is in the internal rack support bush. Adjusting the pinion engagement won't make a lot of difference to this, I would say but I have no experience of rack and pinion adjustments and could be wrong?
There doesn't seem to be any free play or backlash. It has been the same for the last 3 years and maybe before that as well, it gets no worse or better. I plan to try and find a steering rack specialist over the winter and see if there is anything that can be done as I don't have the warranty route option and I am guessing a new or exchange rack is not cheap.