The cv's have a inherent lean stumble off idle. Going to a 50 pilot jet would have made it richer which is what you need. When is the last time you thoroughly cleaned the carbs and verified pop off ? The trick is telling the difference between a lean stumble and a rich bog. There are also low speed screws that are capped at the factory. If you remove the caps, you can adjust the screws a tad to help also.