[Rick Parker]

markha: If you had the carbs apart it is quite possible that the throttle plates did not get reassembled perfectly and it is allowing air to bypass one of the plates when the other is closed. Best suggestion is to view through each throttle bore at a strong light source and rotate the throttle plate (noting the machined notch in each one) until the least amount of light is visable AND the plates are in the same relation with the fuel discharge hole controlled by the Idle mixture screw. The throttle plates must uncover the Idle fuel discharge hole in each bore at the exact same time (degrees of movement) and with linkage syncronized too.
If the leather seals on the outer ends of the shafts are dry or shrunk or the grease in the bearings is lacking it is possible that air can be pulled through the bearings instead of through the carb throat causing an unbalanced reading.