No, they don;t make a lot more power say against a 781 or 049 oval port, like a Vortech would against a 993 or 882 head. The improvements made to the heads, were more for part throttle tq, and emisions, due to imprvements in swirl, and mixture quality at part throttle. The hump next to the guide, and the chamber changes, help with that stuff, more than ultimate power. But, when modified, the heads work really well.
Frank
Advanced Performance
www.get-ap.com