GM Model 700 Throttle Body

[ARTHUR OKUN]

that is regulator output pressure i have a haynes too 
remember that car uses an intank pump that easily will generate 40 psig 
when new  the excess fuel is returned to keep the tb and lines cool.
its not easy to generate those pressure levels without an intank pump
this was  disscussed a while back on this very forum.
question : are you using the mgs original fuel pump does yours 
originaly have an electric one ?   are you using the return line
on the t.b.?