I have also done the mod supposedly changes the ingnition curve to mock the Rs and move the rev limiter back 500 rpm some people don't think it does anything and its a joke but for me i put the jd jet kit in was hitting the rev limiter all the time so did the mod and like it much better (i just move the pink to a dead hole so i can change it back if i want too)
the x useable power is at roughly 8000 rpm but will rev to about 10000. the pink wire mod lets it rev a few hundred more, which will have no bearing on performance.