This is what I did to make mine more responsive:
On the front driver's side of the carb, there is a linkage arm attached to the main throttle. This drives the accelerator pump on intial mashing to "inject" a burst of fuel into the carb. The rocker above the accelerator pump has small holes drilled in it. Re-position the linkage into the hole closest to the pivot and your accelerator pump will react quicker and with a longer stroke.
I'd post a picture, but the carb and the SB it was attached to are all sold
