At low speeds (1800-2400) the engine of my opel seems to be running unevenly giving small jerks. Acceleration is slightly hesitating and the jerks come especially when I take my foot off the gas pedal. Tried to read the fault codes- nothing, gives constantly code 12 (engine ok). When I unplugged the vacuum leading to the EGR-valve the engine runs fine and seems to have more power. Of course the noise of the engine is up.

Could this be a faulty EGR-valve or could something else come into the picture too? The jerking is indeed minor but unpleasant, and I am convinced that the difference in power is a bit suspicious...Could a normally functioning EGR take away that much???

(The lambda sensor of that car has never been changed (at 110K miles), but I do not think it could give that effect....Plan to change it anyway, read that they can get tired even if not giving any fault codes.)