that makes more sense, one pipe to the distributor, one pipe between the 2 carburettors
there shouldnt be any exhaust gases getting to the carbs, only a pipe from the rocker cover to capture and burn evaporated oil fumes.
have you adjusted the carbs so the revs dont drop when you lift the pistons?
have you checked the ignition timing is correct?
Carb calibration and ignition timing are next. I just hoped to have a tad more time before tackling that...