To big of squirters can cause a bog also Is this a three circuit carb? If so try enlarging the intermediate air bleeds .020 or more and go down on the suirteres I had a Holley 9375-2 HP that started to bog, got worst when I changed to bigger squirters, change the intermediate bleeds and pick up .4 in the 1/4,.15 in the 60 ft. times Changed back to smaller squirters and pick up a little bit(.002 to .003) in the 60s