Small holes are supposed to be in the end carb throttle plates.
Sounds to me like you have a bit of a raunchy cam in that thing, and the idle screw is turned up too far which is uncovering the transfer slots. You may need a ton more base timing (14-18*) so you can adjust the idle screw down. You then might find the mixture screws will have some effect.
I actually had to drill some 5/32 holes in my center carb plates to help. But that's with a 270 @ .050 cam.
DON'T do that UNLESS it's neccessary!!!