I fitted mine today...
The part is about £3.50 and took me about an hour to fit, without any instructions and having no knowledge of the bike.
The restriction works by attaching the throttle cable to a different slot on the throttle actutator, this slot is further from the actutator spindle and so the throttle grip still turns all the way but the 'gearing' is changed so the actutator turns only about half way.
The part you purchase replaces the normal throttle cable bracket, specifically the bracket that bolts to the engine and holds the end of the throttle cable tubing. The cable tube has a thread on the end, it fits through a hole in the bracket and is held in place by a plastic nut. It also provides a new maximum opening stop for the actutator.
The only complication in fitting it is that the oil tank pipes get in the way a bit making it tricky to get to the bracket.
You'll need a T25 'torx' key to remove the fairing on the oil tank side of the bike, and the same size 'security torx' key (with a hole in the shaft) to remove the two bolts holding the bracket as these are security bolts with a small stud in the centre that stops a normal torx head from engaging.
According to the two dealers I spoke to there is no ECU or other changes to be made. Mine certainly rides fine and pulls well.
Hope this helps.
