all about the timin'

wusup fellas, i was just wonderin, i recently bought a timing advancement kit for my u.s. lancer and i want to know if any1 else has installed one of these into theirs, if so, what was the outcome?could u feel the diffrence? the guy that sold it to me said there would be gains of 15 to 20hp. let me know wut yall have done. holla.