sucking air sound?

[67cst]

im trying to work all the bugs out of my 67, its only been on the road a couple days and im still getting to learn all its little things, one question i have is when the engine is running i can hear air sucking, its pretty loud too, compared to any other small block ive heard anyways, we took the air cleaner off and covered the barrels to cut off all air flow and the motor almost stalled, i dont think there is any vaccumm leaks, so is this normal? my buddy who is an apprencise mechanic said it might be running lean or there could be a vacuum leak someone and to spray carb cleaner or something like it around the intake etc and see if it revs up at all, anyone have any ideas?

thanks, DEREK