The "warming up" is just the sensor "booting" like a computer booting up sorta-kinda. Basically it just means when the gauge stops reading full lean on start up (I think like 23/24 points something like that) then its "warmed up". The free-air calibration isn't neccesary if you bought your stuff from Dynotunenitrous.com it comes precalibrated - but it is a good idea to recalibrate every few weeks/months. All you do is turn the cars "power" on while the sensor is removed from the exhaust bung (in free ambient air), then follow the series of button pushes/LED readout from the button and LED you wire into the negative lead from the LC-1.