Vacuum Level Question

Take a look at the obvious stuff like carb base gaskets first, as it sounds for sure like you have a leak somewhere.

I assume you are running a PCV valve. So,with the vacuum gauge connected, and the engine running at idle, cover the crankcase breather hole with your hand. You should feel vacuum build. If the vacuum gauge goes up and/or idle quality changes your vacuum leak is internal. Meaning you are leaking at the ports or your intake guides are seriously loose.