What he is saying about the heads is the same as what he is saying about the cam. Everything must function as a unit.

It brings to mind a motor I once sold: it had a larger cam, performance intake and full length headers, and ran pretty good.

The new owner called me up a week later, saying the motor ran extremely poor, did I have any idea why? Well he had stripped off all the performance parts, but didn't change the cam.

I had a less complete comprehension of an engine back then, but I told him the engine couldn't "breathe" and would never run well unless he put the other parts back on, else put the cam back to stock.