Air intake leak between the carb and the pistons action.
the closer the the carb, the more likely.
The engine itself creates Vacuum once it is running.
Sounds like a vacuum leak.
Auto Zone, Chilton shop maual.
http://www.customefis.com/emissions.html
what year is my 350 chevy engine K1201KRH
check for vacuum leaks
Chevy didn't make a 350 engine in 2001
19 to 21 inches of vacuum at an idle, The higher the better. If the engine has a high performance cam then vacuum will be alot lower. When you rev the engine up vacuum should drop and then come right back up.
Atk engines com or 350 Chevy engines com
no
Is the vacume for the distributor TIMED vaume or full vaume at idle???
6 to 8 degrees BTDC / Before top dead center. with vacuum advance pluged.