I’ve been driving myself crazy trying to figure this one out. I have a 2023 CB650R. I recently installed a CS Racing full exhaust system. A buddy recorded a flyby of the bike and we noticed this “thumping” sound that becomes evident as the bike approaches redline. I recently had the ECU reflashed thinking perhaps the bike was somehow backfiring while under load. The problem persists and sounds no different post reflash. Any ideas? It sounds like a belt fed machine gun. The bike rides and operates flawlessly. I can’t hear or feel this thump while riding the bike.