with wild swings of aft at cruise is to possible fuel is puddling in the manifold and then being evaporated into the mixture every now and again? ultimately i would believe that the air fuel charge is falling out of suspension in a dual plane or maybe there is some reversion going on in the intake, valve not sealling all the way, etc? there is a reason port efi is the way to go to minimize variances like this.

i do however applaud your stick-to-itiveness on getting the carb working. i will be following suit shortly and am eagerly following your progress.