VW Passat 1.4: Specifies the primary vehicle and engine type (Volkswagen Passat with a 1.4-liter turbocharged petrol/TSI engine).

03C907309A: This is the VAG (Volkswagen Audi Group) part number for the ECU.

0261S05728: This is the corresponding Bosch part number for the unit.

MED17.5.5: This is the Bosch family type of the ECU, used for VAG turbocharged gasoline engines (TSI/TFSI) that manage injection, ignition, and boost.