What rpm are you shifting at? And what rpm does it start to drop off power? Camel Hump heads if they aren't ported will only let a 406 make power to about 5000rpm or less. Your cam is designed to make power up to 6500rpm. It takes a VERY expensive/good portjob to make camel humps support that RPM. Like the others I would suggest getting an aftermarket set of heads around 200cc intake runner.