It is 100hp midrange increase...not top end...very possible. I mean shit, I high whp (built) B-series, swapping from stock intake manifold to the Victor X, was able to make like 40whp more in midrange just with a manifold swap. Cams are a much more vital aspect. If they can change how the cams open the valves they can fine tune the intake side of the motor much much better. Intake side is the side that either makes or breaks you.