I've heard of others having that issue, depends on the carb, altitude, what fuel you run. My Street Demon doesn't do it much because the bowl vents go into the air horn and the fumes collect in the carb venturis/intake manifold instead of under the hood. If you just plug an external bowl vent fitting then the bowl can't vent properly and when running you'll have weird issues. Maybe not noticeable in terms of drivability but it will definitely throw off your tune.
I'm not a fan of plugging fittings on a carb unless they're vacuum fittings for emissions equipment that's no longer on the car, or for a power brake booster which I don't have because my car has manual brakes.
