maintaining flow away from the exhaust port in the low to mid range is going to bring the most gains. If we can do this without stuffing up the top, even better.
Calvin Elston explains how he views the mass of exhaust gas leaving the cylinder.
Better way of thinking about exhaust than flow and backpressure, or even worse simply maximum flow and resistance at maximum flow. https://www.speed-talk.com/forum/viewtopic.php?t=42375&start=15