Nah, it doesn't feel like the clutch is slipping. It feels like the engine is just bogging down. I can accelerate as fast as I want, it's just that once I hit 6.5k-7k rpms, she just stops producing enough power to accelerate.
i had a friend go through that on a gsxr 750 and come to found out the ram air tubing through the fairing to throttle botties there was a leak. just checked all seals, horns, and boots and anything else that could cause pressure to not be maintained. hope that helps. if not could be timing issues. or electrical.
Sometimes RPM problem often caused by a fuel shortage... Check your fuel pressure.If it's dropping off then it could be fuel pump, filter, pressure regulator.
If not dropping , then it could be spark quality, ignition timing, fuel injectors, fuel quality. Check manual and Set the base ignition timing to factory spec for that engine. What ECU are you using? Does it go lean at high RPM…