Top end loss of power

[Fazerider]

Clutch slippage is quite obvious as it results in a rise in engine revs without any increase in speed, it's most likely at peak torque i.e. 8500 rpm with the throttle fully open. Doesn't sound as if that will be your problem if the only thing you notice is a speed limiter effect.
If the air intake is clear and the fuel supply isn't restricted (kinked fuel or tank breather hoses) then maybe it's the sparks... a TPS check might be worthwhile.