IAT resistance chart
A/C compressor will not engage unless
IAT is over 5C (41F)
Timing will start to be removed at 40C (104F)
The PCM will try to advance timing as far as it can without knock (up to a certain amount determined by programming).
As temperature increases so does the likely hood of knock. To prevent knock before it happens the PCM will start to
retard some timing when the IAT reads 104F. Pulling timing reduces power. So if you want to make sure you always get
the most timing you can spoof the IAT to read a lower temp. But if you make it think that it is less than 41F the A/C will
not work.