it wouldn't cost more then around $100 to get an s-afc tuned, well worthwhile if you aren't looking at doing anything serious. The gains really depend on how bad the state of tune was previously, and how many mods you have done since. You should be able to see a nice 10-15rwkw increase in most of the rev range if you haven't had your car tuned before with abit of boost, full exhaust and an fmic for example.