small block : trying to shift the power band.. 7 "open plenum vs 4-5 "open plenum depths . current depth about 7" .power is best in the upper rpms . I need to drop the rpms so I gain more use of the 4-6 k rpm range and use more of the torque. would this be that much help . don't need a ton . now is best in the 5-7500 range . don't want to change the gearing. opinions .??