s-afc and v-afc's control fuel/air ratios vtec engagement for the v-afc's as well as many other nifty features, they do require tuning but can make it easier to see whats going on exactly. some turbo timers have alot of the same functions which is what i have, and then there are completely adjustable ecu's that u can get from zdyne which cost a pretty penny but are completely adjustable and tuneable from a laptop inside the car. or u can get a zdyne silver ecu which comes preset from the factory with whatever fuel maps, redline, etc you want.