Many people tend to forget that O2 aka Lambda sensors have a replacement interval (in my case 250.000km). Failing to do so will have direct impact on your power and mileage. I checked using Torque (Android app) and checking the Long Term Fuel Trims (LTFT). I noticed that they dropped after installing the new Bosch O2 sensor.
Partnr: 0 258 007 137 / 0258007137