Well I have the Apexi TT

It takes little bit of driving to get the sensor to warm up and read close, but its still not a good tool to use for tuning, but after about 10min the A/F reading should be close

You can also scale the O2 sensor value to give you a more accurate A/F, but I just use the reading for auto mode only

 

I think he's talking about the way the Apexi TT reads the O2 sensor to determine how long for the car to idle. But either way, it won't work...

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I would not use the A/F on the TT
Its not accurate

If you want a good tuning unit get a Wideband O2 setup

 

No it won't you need a wideband O2 sensor. Check out TurboXS.com