i have a 73 nova 350 4 speed with a tunnel ram, 450 Holley's. i had the same bogging problem. i found some answers in a Chevy high performance mag. aug 2006 in performance q&a sec. it says to use some stainless steel mechanics wire put a small piece in each main circuit air bleed, located in the venturi area above booster. make them long enough to bend down the outside of the carb. idle air bleed is located toward the out board side of carb,the main is toward the inboard side. i use my vacuum advance and my timing is set at 37 total with vacuum advance off and plugged. they give a complete setup in the book. i would call and order that issue. or i could e-mail the article to you.