In the June 2011 issue of Eurotuner magazine there was a tasty S4 B5. The modifications were extensive, highlights included an increase in capacity to 3 litres and the main upgrade, an Agtronic turbo kit.
We had never heard of Agtronic but we checked out their website and the quality of their work seem to be top notch. The S4 featured in EuroTuner was knocking out 588whp with the use of GT2860RS AKA Disco Potato turbos. There is probably a lot more to come from this engine with the use of bigger turbos but if you want a response machine it’s probably perfect