The german tuner Wimmer has the stage 4 kit ready which brings the horspower up to 408 and the torque is astonishing 540 NM
http://www.wimmer-rst.de/fahrzeuge/pdf/2,0l%20TFSI%20S3%20265PSOrange.pdf
http://www.wimmer-rst.de/fahrzeuge/pdf/2,0l%20TFSI%20S3%20265PSOrange.pdf