Intake distribution issues

I run a carb so this may not apply.
I briefly ran that intake on my 360 with a square flange plate, 1" 4 hole HVH Super sucker and a 750dp carb. 3, 6, 7 cylinders were rich. I swapped to a Victor 340 square flange intake and 3 & 7 are rich. Car runs great with either manifold but I'd like to get the plug color closer.