Find the biggest needle & seat,or make it as large as possible,if your float bowl area is small,like on Webers.
You need a float that will not collaspe under boost pressure.
Float that is made of plastic or fill your brass float w/foam then reseal it.
Throttle shafts can leak.Accel pump,idle adjustment screws etc.
Or enclose the entire carb,then you do not need to worry about leaks.
here is some good info: http://www.vs57.com/carb.htm
If you use a holley 2 bbl or 4 bbl carb they have aftermarket parts that I mentioned.
A boost reference hose to your fuel regulator,top side of diaphram.
Probably need to mess w/your needle & jets.
Good Weber carbs usually do not leak on the throttle shafts,they have roller bearings & seals on the shafts.

MBHD

12 port SDS EFI