I think I found my off idle stumble. The accelerator pump wasn't doing anything. When I attempted to adjust the arm, it was at the bottom of the stroke already. No spring pressure. Pulled it apart and found nothing put of the ordinary. Diaphragm wasn't torn and spring was good. Not sure, but the replacement from another Holley carb has the spring pressure as it should. Need to clean filter and try tomorrow. With no pump at all, it would explain the lean spot. Also need to readjust the front brakes. Then try driving again. Bit by bit...