We try to get the IT probe in the vicinty of air of a similar temp to that being consumed by the engine, so in the cell close to the car is good, but not in the engine bay.

If its in the engine bay itself, the air is much hotter there and not a true reflection of the actual intake temp because the air going into the engine hasn't been in the engine bay long enough to get that hot. That's my slant on it anyway.