Originally Posted by Bariga
3 inches from throttle in IC pipe
Ultimately you would want your IAT sensor as close as possible to the Intake valves. EG.. In a runner very close to the TGVs.
When you have it in the IC pipe with the throttle closed the small amount of air going into the Intake manifold is still going to be heated up A LOT due to slow movement and a hot engine. This results in inaccurate measurements when idling for a while with a closed throttle as you mentioned.