Brad......refresh my memory.

Doesn’t the stage 6 manifold really have MW sized runners, and is shrunk down where it bolts to the heads?

That’s how I remember it.......but I haven’t looked at one in several years.

If that’s how it really is, and one was looking for the “next step” in improving the flow into the motor........I would think opening it up, and then making the heads MW size to match would make the most sense.
I think you’d probably have to make a step up from the 509 cam to really see much benefit though.