The engine in the A6 will have only 230hp vs 264 of the S4's engine. Still runs to 60 in 7.2 seconds with the manual tranny. I suspect the ECU can be replaced by the S4's for a quick/easy 34hp shot. Then do bigger IC's, bigger exhaust, redo the S4 ECU, and bingo, 450hp+ safely. -Eric Ferguson PS: also rumored to have a 2.6L TDI coming soon