Back when the vacume pump systems where being introduced into drag racing most of the dyno tests done on a A,B,A test basis found that most vacume pump system didn't gain any measureable HP below 6000 RPM, this was on both BB and SB Chevy motors of course. The higher the RPM tested the more HP gained I have a 3 vane Moroso vacume pump that I am planning on using on my next BB Mopar all out stroker, 555 C.I. , bracket race motor build I'm shooting for 15 to 17 inches vacume at the upper RPM, above 6000 RPM probally, shifting at or above 7400 RPM