OK... last one because I see a pending disaster on the horizon!
Don't even think about hitting that with a juice unit the way it is. You'll kill that thing with fuel which contrary to popular lore, is a BAD thing.
Get a pressure regulator for BOTH side, carb and juice. They will likely take entirely different pressures to operate correctly. Set carb side to 6-7 psi.
Change the rear outer bleeds as 805 laid out. If you have a 1-60 drill set, you can do it yourself. Try anything from .070-.075.
I'd bet those two things will make a world of difference.
One other member just told me he had a carb like that one and it came with smaller IAB's in secondaries. So maybe your friend didn't monkey with it. First one I've ever seen. Fricken holley must be dropping acid on a regular basis to install those.