FWIW, when I did my CAI, I took the outside temp sensor and relocated it to the fenderwell right beside the air filter. I have tested the accuracy of the sensor and surmise it is within 5 degrees of actual temperature. I generally log the temperature reading each run down the track.
It generally shows 10 to 30 degrees above ambient air at the track. The hotter the ambient air, the larger the difference. I have seen it within 5 degrees of ambient temps on cooler days and as high as 40 degrees above ambient temps on the hottest days - depending upon how much cool-down time between runs I get.
It would be interesting to see how that compared to actual IAT readings.