I also run a Holley DP. Love them. I chased a similar problem (idle adjustment) for a long time. Finally just learned to live with it. Two summers ago I was changing to an open plenum spacer and had the carb on a stand on my bench. I was visually inspecting all the external linkage and discovered that the choke fast idle screw (the one you can't see behind the choke heater) was not in alignment with the fast idle cam face. This allowed the adjustment screw to go beside the cam. I would never have seen it while on the engine. A slight tweak with pliers and all my problems were solved. I am not saying this is your problem but I am saying the carb has many points of adjustment that have to work in unison to achieve the desired outcome. Before you tear into the carb make sure all the parts are working correctly. Been dealing with Holley carbs since I bought my first Corvette in 1966. I like them alot. PS: the Open plenum spacer made a HUGE difference in driveability. Good luck.
Krusty
Krusty
