Dart 351/427 with Quick Fuel 750. On cold start, RPM stays at fast idle until it starts to warm, then will slowly drop to around 500 RPM for a second or two, then climb back to 1500 +/-, stay there for several seconds, then drop again, and rise again.
Haven't started looking into it yet, but will start with base timing, then move on to mixture, etc., but am open to suggestions as to what could cause this and where best to look.