Just a thought, If you have larger than #6 lines ( #8 ) supplying the bowls like you did with your single carb, that required them. The larger line will cause a significant fuel pressure spike if a front mounted fuel system is used. This condition is necessary to keep a single carb supplied with fuel at the bowl during launch. With dual carbs the fuel consumption is 1/2 per carb now and the fuel spike at launch could be giving a dose of fuel it can not use now or control. I would run near 6.2 PSI with dual carbs and #6 supply line and NO FUEL LOG. These things can cause problems that the other set up needed to run correctly. Go back to the 2 flats above level or set them on the bench with a 3/8" drill bit or piece of bar stock like you used to. The lower fuel pressure is easeier to control and can easily keep up. You will know if it is lean due to the lower fuel pressure because it will drive to the 100' where you are unable to get to now, but it will be fine. 6.2 is high pressure for dual carbs with .375 float settings.
More things to ponder.
Bruce