Welcome to the transition nightmare!. You are right there in the zone between 2500-3000. For me it was during moderate acceleration in that zone. I could usually blast right thru that stumble during WOT throttle. I used to watch the AFR go up to 16+ and then the stumble. I played with my bleed pipes that were inside my emulsion tubes, but not sure of your set-up. I finally started filling the bleed pipe holes with solder with good results. I had tried everything else including float levels, pilot jets, pump jets and settings, main air jets, main jets without much luck. I would push the pilot jet as far as you --even running 12 afr at idle and see if that helps. You need to remember that you are dealing with many variables with triple sidedrafts-this isn't your quadrajet. These carbs weren't meant to be daily drivers as much as they were for racing. Todd at Wolfcreek could not offer much more help then getting the carbs tuned for racing. When I would describe my transition issue he would say you have them running pretty good if you ask me. When they run good though.... https://youtu.be/NGh6urUlzcQ