I'd love to see how my Chapman 285's would do on that block against the EZ-1's. The chaps are well known for the intake flow but with a 2" tube they flowed close to 300 @ .700 on the exhaust with the smallish but apparently very efficient port. It'd be an interesting comparison for sure, I suspect you're at the saturation point of the exhaust where it's simply slowing down the pumping rate (ability to keep accelerating) at high RPM which in turn limits how much draw you can N/A draw on the intake almost regardless of flow potential.

They'll say the exhaust just isn't as important and it's not at moderate piston speeds and RPM's but sooner or later you slow the pump down when you can't get the air out quickly enough, more valve timing can help to a point but eventually. with a 500 inch motor it's like using a piston to push fluid out of a filled 1 litre bottle...if one has a standard opening and the other has a Mickey's wide mouth, at some point, sooner or later Mickey's gonna win.