We wanted to show the difference between the two pulley drive combinations. The eight-rib pulleys with a smaller supercharger pulley increased boost from 15 psi to 20.5 psi. The real story is that this engine makes peak power at 7,200 (stock cams and stock intake) and peak came at just 6,600 with the six-rib pulleys because the belt slipped after that point, bringing boost down to 13.5 psi and hurting power. The boost was at 15 psi for the peak power output with the six-rib configuration. The eight-rib pulleys did spin the supercharger harder, but the belt didn't slip and boost shot up to 20.5 at 7,200 rpm for a peak power rating of 1,032 rwhp.