Twincharging
The method of turbocharging and supercharging an engine is referred to as twincharging. This technology is very rarely used because most racing restricts to one means of forced induction, and rarely on road cars as its benefits lie mostly in the realm of boost curve fine tuning (quicker boost response) and allowing for said with the use of a freer flowing turbine/housing spec on the turbo to make it more efficient (or less inefficient, compared to the tighter housing needed to minimise lag) at higher rpm. Such twincharging does still see use in some hillclimb racing, where throttle and boost response are paramount over peak power concerns. The S4 itself, when everything worked perfectly, managed to hit 2.2 bars (32 psi) boost.
Nissan produced the March Superturbo in 1987 which was also both supercharged and turbocharged. The most recent application of twincharging is found in Volkswagen's 1.4 TSI engine, launched in 2006.
Read more about this topic: Lancia Delta S4