I have been wondering about calibration accuracy on my LM1. Wouldn't having a free air of 20.9% mean that the wideband is accurate? My exhaust is huge & straight through, so every once in a while I before starting the car after it has sat for a week or more I turn on the WB & let it set until I see the 20.9%. Is this good enough for checking calibration? TIA for any input.