95 s10 blazer fuel pressure problem

I have a 95 blazer with W engine and CPI injection. It wasn't starting right so I took a fuel pressure test at the shredder valve. with key on engine not running it had a pressure of 62 - 64 psi., but would leak down fairly fast. I took the top of the plenum off and the fuel pressure regulator was leaking out the hole in the side.
So I bought a new regulator (a Standard PR484) and put it on and now no leak and slowed the pressure bleed down to a very slow bleed off. But now my pressure only builds up to 54 -55 psi, key on engine not running.
I don't know why I'm only getting 55 psi now when it was going to 64 psi before the new regulator. I looked up the regulator on the internet and it says it's for my vehicle.
The book says it should be 58 - 64 psi.

It has a screw in the middle, I don't know if that is some kind of adjustment or what.
I had one guy tell me to adjust that screw to get my fuel pump pressure at the shedder valve back to 64 psi.
Is that right ?

It seems to me that the regulator would be for adjusting the fuel pressure going to the poppets at the cylinders, and the fuel pump is what dictates the fuel pressure at the shedder valve. But I don't know for sure.

Thank you very much for the help.