Im sure others will disagree but Im confident they are not useful. They do let the motor rev higher but well before that, the motor was ready to be shifted to the next gear. I've dyno'ed them my self and have seen a 10th of1 hp here and there added. IMO not worth the $50+ they are.
The inner rotor ignitions are only $35 shipped and make a world of difference.
Yes easy to install and definAtly have some cheap ones and some nice ones I'm tryin to sell my kitaco type 1 inner rotor kit now 810$ new only want 250$ maybe has 5 hours on it revs the motor completely different and let's you mess with the timing a little sounded like a big bike Actaully just wanted street legal now so had to go to stock for the lights.
i have the tokyo box and it makes your throttle response way better, i found they are way worth it when hitting the track because they you get up to speed alot faster after railing a burm