AFR Blue Hornet Mopar cylinder head, Charles Servedio

Sounds much like the effect of a pushrod pinch. Or in another way a flow ball.

I have done a good bit of flow work with the same manifold he is using and basically the same head (ProMaxx and Speedmaster), but I have never put the manifold on that small of a port. With a head that flows 290-310, it is not uncommon to see a 20 cfm drop in flow on the top end. I've never seen an increase at those flow rates.