The factory used a special ported vacuum slot for EGR, with a bleed-off port so it doesn't fully open the EGR valve at light load/light throttle cruising. Make sure your carb has the correct port, it as in the baseplate, passengers side on most models.
The correct ported distributor port is on the drivers side, front of the main casting to the right of the fuel filter housing area.
Since you are dealing with a "remanufactured" carburetor and not a rebuilt original unit, many items inside the carb may be altered, or not factory sizes. They also miss-match components, so it's not surprising the carb is out of spec.....Cliff