I would pull the needles and seats and see what size they are, most of the OEM Holley needles and seats have the size stamped onto the side of the top of the slot on the seat where the locknut and lock screw fit into I reread your post on the engine combination, what are the BB Chevy cam specs, duration at .050, LSA and lobe lift BTW, if the engine dyno shop your going to use doesn't have a wide ban AFR sustem on it find one that does There are , usually, three different fuel sensors that will tell you info on the fuel delivery(GPH), fuel pressure and fuel consumption, BSFC. The wide ban will tell you about the amount of O2 in the exhaust, 12.3 to 13.3 has worked well for me on N/A pump and race gas motors, depending on the motor, compression ratio and fuel used Good luck, there is a reason when parts don't perform as well as they should, the hard part is figuring out what is wrong