i also know that GIAC makes some really good performance chips!!!!! i'm buying the triptonic, and comp. chip. the triptonic is increasing my shifting about 75%, thats pretty damn good, instead of taking a sec. to shift it's gonna take me .25., but i have not checked on wat they have for the S4, but i'm sure they have even more parts for u'r car b/c i drive a 2.8L V-6 A4