Bo,
Four more horsepower is a significant increase, especially considering the minimal changes you have made. Unfortunately, you and I and most people end up making several changes between runs (dyno or salt flats), so we don't really know which change made the biggest, or any difference. Such is life.
I, too, have a pumper carb, and was plagued with bogging between gear changes. I blamed it on overly large intake passages (velocity too slow in ports?), but I don't really know. I went from 36mm ports to 40mm, so maybe too much change at once. Such is life!
Tom