Here is an interesting one. My 327 with a Holley 4150 600cfm will not run from 1000 to 2000 rpm's. There is just a dead zone there. If I slowly advance the throttle, the rpm's will stop advancing at 1000, even as I advance the throttle, but then suddenly jump up to 2000 rpm. It does this even if I adjust the idle speed into this "zone" and let it stay there. When I go back down the same thing happens, the engine will suddenly drop from 2000 to 1000rpm but not run anywhere between. Is there some kind of transition circuit that operates between the idle jets and the main jets?