The best factory head that never was

The one thing I don't like about the 308 exh port is that its always turbulent or noisy on the bench. I get great flow numbers out of it, but often wonder if its really working well on the motor ????? Years ago I tried opening up a set of 308 exh ports to gasket size. While the ports quieted down the flow took a 20 cfm hit 205 peak to 185. Would love to dyno test a 450-500 HP range motor with these heads done both ways.