Launched in `1999`, the `RS4 B5` was the first true `RS4` and immediately established Audi's formula of the ultra-fast estate. Against a more radical BMW M3 or a harder-hitting Mercedes C-Class in `AMG` form, it played the card of big torque, permanent `quattro` traction and exceptional versatility for the era. Today it is a very desirable youngtimer, but one that does not tolerate approximation or budget-grade maintenance.
Its known base is the `2.7 V6 biturbo` from the `S4 B5`, heavily revised with specific heads, intake, cooling and turbos to reach `380 hp`, always with a `6-speed` manual gearbox. The engine pulls hard from the mid-range and the driveline copes well when follow-up has been coherent. On a car of this age, however, value depends above all on the quality of the work already done: timing belt, vacuum system, sensors, cooling, suspension and lubrication history.