While that may be true on some of the newer setups, boost is achieved incrementally by RPM's on a supercharger, unless you're using one with a bypass valve where you can push maximum boost in the lower range because the boost levels are low.
I've been using older model S/C's on V8's during many of my earlier days, but that was pre-Vortec style, such as the original GMC, Weiand, etc, so my tech might be a little out dated on newer setups, but I usually don't mess with low-boost applications (below 15psi).
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