Steering Pinion Valve Leak
 

The diagram is of the Rack of a 92 xjs. It shows the Rack and Pinion and the Valve in which I have a leak. The leak is coming from that bolt, which I believe is called a set screw? I'm not too sure, it is a big nut though. The second 2 pictures are looking forward from under the rear of the car, the last one is looking towards the rear from under the front of the car. Could there be a seal in there? Or a washer that needs replacing? There is no fluid anywhere else, you can see a bit of the boot which is dry as well. I am trying to figure what it is I am looking at. There is a drip, still hanging off that bolt. As always, any guidance would be appreciated. And what is the trick to pushing those caliper pistons back? Mine won't move at all, doing it the traditional way anyway.

Not sure about your rack, but pistons should squeeze fairly easy in, while pushing other ones out. You might have much of deposits on the bottom of brake pistons, but these are not hard to take off and take apart. Also, rebuilt kits are dirt cheap.

First off, I suggest your calipers need a rebuild with new seals, and (probably) new pistons. Car is nearly 20 years old and these things dont last forever.

From your rack pics, you are looking at the other (blank) end of the pinion housing. You will see a little screw in the middle, which covers a hole for a special tool used to set the rack in the correct position when assemblying the steering system, although the blunt end of a drill of the correct diameter also works (this is what I used once).
The set screws are holding on the cover plate which blocks off the machined passage for the pinion. Could I suggest you remove the set screw and refit with some thread tape around the threads. This might seal it up. Of course the leak may be elsewhere, and as the setscrew is the lowest point, this is where the fluid is ending up.