what are the advantags of a vtec controller? will it make my car more fuel efficent?

Answer 1

It lets you change the RPM where the VTEC switches on. It's most useful if you have modified your motor either with aftermarket cams or so many other mods that the transition to VTEC becomes jarring.

It is not a good mod for an otherwise stock, or nearly stock (cold air intake, exhaust, headers) car.