I first off would recommend a double pumper for your application.
It sounds like you got an all out race motor on your hands and well I vacuum secoundary carb just aint gonna give you the performance you'd get out of an double pumper.
Back to your problem.
The secoundaries on a vacuum carb don't have jets like the primaries do, it has a metering plate, its a weird set-up to say the least and I'm not really "UP" on them but it sounds like you might have some blockage in the metering plate itself, remove the bowl and you'll see the meter plate on the back of the carb center section, remove the even weirder metering plate bolts and clean the plate out real good with some carb clean and compressed air, remember to blow out the feed holes in the carb center section as well.
Goodluck, Cp