Normal
Another thing will cause stumble off idle, the sync being off at higher RPM. I used to first bench sync, then idle sync with a hot engine and then sync at 3K rpm to verify all carbs are pulling the same. One time I had a good sync at idle, but could not get a good sync at 3K plus there was a stumble when I flipped the throttle. Turned out to be a sticking carb slide.
