Inlet restrictors are used in the UK to allow large bikes to be ridden by new riders.
They limit the bike to 33hp.
Don't know of any "superbike" that has the restrictors though as it likely will make it lumpy
Limiting using the ECU woudl never be allowed as it's just TOO easy to remove the restrictor for short periods of time !! So can't see the insurance companies accepting it.
In the UK most folks don't really bother de-restricting a bike as it's easier to just buy a bigger one
"A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'