Draw through slant six turbo setup

Does your turbo have the proper seals for draw thru? Where did you get the plenum to mount the carb on? The early (as in, before GN) turbo Buicks were draw thru, and had an electric heating element to keep the carb from icing. I think they were all Qjets tho, so you may not get one to work with your AFB.

May I ask why you decided f/i instead of a mild n/a buildup?

Best of luck!