sct is the way to go. theres alot you can do with just the x3. you can change idle speed, adjust the spark. few basic stuff. but tuning is not for everyone. if you plan on tuning a car yourself go for the sct software. little pricy but pays off if you add alot of mods. but you need to know alot. ive watched instructional dvds, read 3 different manuals and have a spiral notebook full of notes and still end up wanting to shoot myself after looking at all the numbers for hours on end. oh and one wrong key stroke or math error tuning can blow your motor real quick.