Stiffening my power steering?

Would a restriction in the high pressure line from the pump to the gearbox reduce the amount of "assist"? or reducing the amount of tension on the pressure relief valve?
I'm just guessing but my rationale is that if there is lower pressure then there is also less assist since the pressure is what drives the gear...

...Nevermind, i found the Mopar Muscle magazine article where it says that the steering resistance is set by shims .....

"The eventual firmness of the steering system is adjusted to each customers' tastes by different thickness of shims (arrow), which are installed after the preload adjusters."
taken from: ( bottom right picture )
http://www.moparmusclemagazine.com/..._0209_rebuilding_your_steering_box/index.html