holley 3810 problem

[ssl78]

I have a 3810 Holley carb I rebuilt, it did have a 1/8 in hole drilled in each primary throttle plate. The carb works well except at low end steady throttle fuel is only coming out of one main venturi and I feel a lean miss on one side of the exhaust this is a Corvette and has side exhaust at higher rpm both venturis have fuel. I never ran across this before any body else ever have this happen? Any ideas why? . I did check both air bleeds and they are fine?