Speed starts at 9000 revolutions and closes at 140km/h

Good morning, newbie here and no expert in engine technology, so please forgive me in advance 🙂 I have the following problem: If I am with my Suzuki GSXF 600 Bj93 at approx. 9000umdr., the speed is slashing and there is a misignition sounding noise 😉 After approx. 2-3 and some gas removal you run again as if nothing had happened. Lt. The previous owner is the machine has been throttled about 3 years, is also registered with full PS number (86) and runs also b is 9000umdr. normal. I guess it’s a problem with the throttle, since throttled motorcycles just close in the speed range up to 9000umdr. and up to 140 km/m. Does anyone know this phenomenon or has a solution proposal? Greeting Erik