OK, well if he does it, then it makes no sense for you to add any shims.
This may have been said: I don't expect you see any change unless your present HV pump is worn or has a lower pressure spring or a whacked out part. It will keep pressures up at the lower RPM's better if the clearances are tighter but the relief spring is what limits the upper pressure.
I understand. At this point, I'm not expecting to see any changes either. But it's already on it's way, so once I get it, it's going on when I change the rear main seal. You'll be hearing from me. Lol.