If more pump shot helps then that is telling us that the transition circuit is very lean. We need the huge pump shot to cover up the hole in the transition slot. What we need to do is make the idle and transition circuit richer. Where is the IFR located in the metering block? High or low? also how far are the 4 corner screws turned? Is the transition slot square? Turn the carb over and open the blades so the transition slot is showing a square with the blades.

If you get a rolling start say 3000-3500 rpm and mat it to the floor does the bog still exist? Is the bog only from a low rpm start?