Newer Holley carbs have power valve blowout protection. You should continue to tare the carb down. Pull the float bowl(s) and document the jets. Pull the power valve and document the value. You may have a higher value power valve and low idle or part throttle vacuum which will cause the power valve to be open more that it should. This would cause an overly rich condition.

Your power valve value should be 1-2 lbs lower than the vacuum recorded at idle when the engine is warm and the car is in drive (automatics only).