AFAICT the Carter P90091 pump runs continuously and probably just regulates pressure with a built-in relief valve that diverts excess pressure back to the intake end.

On another car running that pump I'd added an inline pressure gauge on a Tee off the supply line to the carb, can't say I've noticed any pressure drop there. Make sure your gauge points off sideways rather than straight up, as the latter mounting could trap an air pocket that may result in odd readings. Did you plumb in a return line, or is it just dead-ended at the carb?

Anyway, Webers don't need any pressure, just adequate flow to keep the float bowl primed. Max. pressure spec is just to avoid forcing fuel past the needle valve when the float should be holding it closed at full-bowl.