Ootb Stealths Flow right around 260 on my bench.

Recut the seats, back cut the valves, blend the bowls and SSR, they’re basically right at 280.

Whittle down the guide boss, open the pinch a bit, relieve the chamber wall adjacent to the intake valve....... puts it right at about 290.

I suspect that from that point, increasing the size of the opening to MW size would be worth less than 10cfm.

The set from the pic below went on a build that was going to be using a factory x-ram.