I saw a 30 HP increase going from a single Holley 1050 CFM Dominator carb. on a Indy 440-3 intake to two of the same list # Holley 1050 on a Indy M.W. tunnel ram intake with no other changes
I also tested two different sets of heads on the same short block using the same intake and carb, that was with a set of Indy SR M.W. heads and a set of ported 440-1 heads that flowed right at 30 CFM more on the 440-1 heads. My old pump gas 400 stroker motor made 727 HP with the SR heads and 775 HP with the 440-1 heads with the same compression ratio, both heads had 76.0 CC combustion chambers
Their was a issue with the dyno headers on the 440-1 heads, the exhaust port on the 440-1 heads where slightly bigger on the exhaust port floor than the headers where(1/8 to 3/16 inch step into the headers ), which would make the motors start to have a slight random miss above 5200 RPM