The big carby always brigade misses the simple point that a smaller carb can change numerous things such as distribution [ A/F ratio for each cyl ], droplet size etc such that the smaller carb could make more power. Bigger carb is not absolute on every engine. Look at the old MP mods to intake manifolds with popsicle sticks to try & fix uneven A/F ratios in the runners. Try a different carb, these mods might not work.