This Audi S4 (C4) wagon was built by WALAS MotorSport in Mokrawica, Poland. Under the hood sits a 4.2 L V8 (ARS) from an Audi A6 (C5) flanked by two GT2871 turbochargers producing 587 horsepower and 805 Nm (593 lb-ft) of torque. The engine features TECHNO5 forged rods, 80 mm throttle body, and Audi RS6 (C5) intake manifold. A Bosch 042 pump sends fuel through 630 cc injectors controlled by an EMU ECU. The engine mates to the S4 O1E transmission with an organic clutch. They upgraded the brakes with Porsche calipers.
Source: WALAS MotorSport FB page