I have a GM crate 350 in my 55.2 Chevy truck. It has an Edelbrock 600 cfm carb on it. I have this problem where it starts and runs fine, it revs up fine. But if it is at idle and I flick the gas half way the engine hesitates as if it ran out of breath or something. I am an amateur when it comes to carbs. I had the same problem with a Ford Mustang with a factory carb on it. Someone suggested a vacuum leak, but there are three vacuum tubes on it and all are in good shape.

Any suggestions and/or education?