High IAT will cause the ECM to retard timing (and probably other things). IIRC, it starts backing off around 85-90F. I've noticed some lag/bog in stop-and-go traffic in the Summer. Usually clears up once I get moving and measured IAT drops to closer to ambient. There does appear to be significant thermal mass to the sensor and/or housing as it takes a while to drop.
My IAT reads 6-7F high but it hasn't been a big problem for a DD.
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