Fast Idle Lambda Check failed twice: 1.039 and 1.035. On the same printout the readings on both fast idles for CO and HC are 0. For natural idle CO is again 0. On previous MOTs and at the same Test Station (which has changed hands) I have always had readings other than 0 for most of these parameters, though within limits. Is it possible that the test was at fault here rather than the car? I declined the offer of a £50 diagnosis and removed the car, thus losing the chance of a free re-test, as my instinct told me something didn't add up. Was it right? What else can I check?