I dont know what the flow numbers on the heads are. They should be more than you had before at your cams lift points with the old heads. Issue the intake manifold dosent flow more and is choking the air flow. Your next move should be a better flowing intake. A Torker II might be a good choice if the ports are not raised port heads. Should pick up about 30 CFM a runner. Educated Guess thats about 70 HP. Ty it with the small carb first. The exhaust side you need some headers.