Problem - Car is all of a sudden idling very high. It is definitely a vacuum leak but where do I start looking.
Possibility 1 - Check all vacuum lines, connections, adapters etc to see what condition they are in. Look for cracking or loose connections.
Possibility 2 - Plenum chamber gasket may be leaking.
Possibility 3 - Spray some carby cleaner or aerostart around each of the connections. If the spray finds a leak, the engine RPM will increase for a couple of seconds. The spray makes the air/fuel mixture go from being lean to rich.
Possibility 4 - If you find a line that is cracking or perished, replace that line and you may as well replace all the others as they may be perishing also.