I have a 73' 350 firebird motor in my 80' cutlass. I only have 5 inches of vacuum. It has a ram air 3 cam. I noticed that when looking from the front of the motor there is a hole in the valley pan on the left side of the thermostat. Is it supposed to have a pcv valve or something in it. Could that even be the source of the vacuum leak? I've spaying carb cleaner around all my vacuum fitting and my intake gaskets with no luck of finding the leak. Any help?