Track down a vacuum leak?

[njsteve]

If its the original 69 with a Quadrajet it has the two piece carb to intake gasket. One piece is the thin metal heat shield and the other is the gasket. The metal heat shield goes down first against the intake, then comes the gasket. If you leave the metal shield out you get a vacuum leak from the heat riser. It usually wont show up when you spray the carb cleaner around the base plate because it's sucking vacuum from inside the engine not from outside. I would pull the carb and verify the correct 2 gaskets are in place.