The "fast idle cam" is what effects the RPM's when the choke is engaged (cold engine). It looks like a stepped arm on the passenger side of the carb. There is a screw that adjusts this setting. When I originally put on my quadrajet the fast idle arm was wedged way up so the car would "idle" at 3,000 RPM! Here is the description on how to set it ("borrowed" off a Corvette site):
FAST IDLE ADJUSTMENT
Close the primary throttles and position the cam follower above the high step of the fast-idle cam. Turn the fast-idle screw clockwise until it touches the lever then turn it down three full turns. Readjust the fast idle rpm with the engine cold and running (choke closed).
This page has a drawing showing where it's located:
