I maybe off on this since I did it in 1966 but I remember a Carter AFB that was standard equipment for a Pontiac that controled it's idle with a large screw centered on the front of the carb. With a non stock air filter it did whistle and sounded a lot like a Rochester FI unit. I had one on my 62 Chevy II I put a V8 in in 1965. I later got a 1961 FI unit so I could hear the whistle for real...That's one coupe I wish I had back......JD
