well, less vacuum in drive is normal. 1-2 turns is spec, so your in spec and at one turn your idle circuit(IFR) sounds rich enough. You will loose vacuum when the screw is too far out as that's making your engine unhappy. I would still have a look at that secondary vacuum pod. One other thing to check is the secondary blade adjuster screw. It may be right out where you can see it or could be under the throttle plate. If under the throttle you will need to remove carb, flip upside down to adjust. You will have to look up spec, but you don't want those secondary blades open too far at idle.