Where'd you get lambda sensor and how much? If it's not that it's an expensive waste of money isn't it. When i thought there was a problem with mine i got it checked using Ecutek Deltadash (i think it was) and the voltages were apparently OK so i didn't bother replacing it in the end. I'm the opposite of you - a lambda of 0.96 and fail - didn't bother bringing it back since even after being stopped at checkpoint by guards who asked about the NCT missing...