is the aem fuel pressure regulator that mounts to the rail a bypass type regulator?

 

return and or bypass yes.

 

a blocking style regulator "regulates" the pressure on it's outlet side. (used in-line before a carburetor)

a pressure relief valve "relieves" or "regulates" the pressure on it's inlet side. (typically used on outlet of fuel rail for fuel injection)

you won't find a blocking style regulator for fuel injection.