Its already been described how to do the adjustment. I have been through allot of engines/injection pumps in my short vw career and had to deal with terrible worn out bushings once, ditched that pump for parts. You could really tell by rocking the sprocket.
Most of the other used injection pumps I have come across that ran I take apart and clean and reseal and run them, I have extras on the shelf.
I have found from my working stash when swapping pumps and doing a timing belt job from engine to engine without changing anything else, for the timing belt tracking to change.
Once you know your engine and look under the hood of a used car you can tell if things are being neglected
But you can get your belt to track, I have had to readjust before and it can be annoying to yank the pump multiple times. If you move engine front bracket to much you can go to far, so I like to do a bump at a time with the bolts cracked.
Thats the way I do it, let the timing belt decide. I also use those im shafts with no lip. So inbetween each change, hook pump up without timing it and crank the starter over a good bit to see where things settle down.
Also I move my setup to tdc so i can put pump lockpin in and then clamp each pulley to the timing belt and the injection pump sprocket to the bracket.
Don't move anything and you can just start the keyway on the injection pump on reinstall and tightning the bolt to spec will pull and guide the sprocket to where it needs to be with no clamps on at that point. I have done this many times and checked timing after and it seems to work ok vs. doing a full timing job again?
Experts need to chime in on that procedure and what they think about it. Somebody in passing mentioned this to me years ago and I tried it with the vw timing tools to see if it would keep everything in relation and I haven't had a problem lining up tdc and the locks?