I see the exhaust flow, more the merry route, helping relieve the pistons ride up the cylinder with more ease as the port becomes more effective. To start with. Then from there, I s about cam timing events.
You can’t ignore blow down and pumping losses. I do know that making the exhaust port flow more at the expense of shape and sound on a flow bench is a power killer. Had to learn that one the hard way. The flow bench will reward you with big flow numbers the bigger you make it. If it gets noisy you can bet it will lose power.
