The article presents the results of engine tests aimed at assessing the impact of modifications to engine control software on emission parameters and fuel consumption. Experiments were conducted on a 1.3 L MultiJet compression-ignition engine compliant with the Euro 6 standard. The electronic control unit's EEPROM was extracted and re-calibrated by a leading chiptuning company. Two operating scenarios-factory calibration and the modified calibration-were executed on an engine test bench equipped with a dynamic dynamometer. To ensure repeatability and comparability, the dynamometer governed engine speed and load in accordance with the New European Driving Cycle (NEDC) homologation procedure. Analysis of the revised calibration maps revealed substantive alterations, chiefly to the boost-pressure characteristic, the maximum-torque map, and the maximum fuel-injection-quantity map as a function of air mass. The resulting emission data demonstrate that chip-tuning exerts a pronounced impact on the engine's emission profile, elevating the release of toxic exhaust constituents, most notably nitrogen oxides.