Disappointed with my engine

Isn't it true the carb will only air flow what the engine pulls or needs? Also I thought it has been said that you double the displacement for example a 340 X2 = 680 that's what size carb or you could run a 700 cfm carb. as a starting point...:)
if u r turning 6000 rpms then a 750-800 cfm i used a catrr thremoquad on my 400 i was turning 6-6500 i also had 95# pf oil presure (there is a rule of 10# of oil pressure for every 1000 rpms) if u run lower oil prssure u run the chance of staving the bearlings of oil. i have seen guys blow mopars up. but do as u like i really dont think fuel flow is the isse i thonk the camshsfy dose not match the rest . i only used mopsr performance cams Now how much faster do u want to be?