Used searched but no results ... a mate from Italy has a late Diesel with the MAF sensor, and his HawkEye shows a "Boost Temperature" reading fixed always at 124.8 deg. Vehicle has no strange behavior, fuel consumption in the norm, smoke, all seems fine, but the weird data remains.
He tried swapping MAF with another friend same year/model but no change in the data observed. Unfortunately don't have access to a Nano or other means of checking (actually, do these phony things app like Torque work on P38s?).
Anyone has come across a similar case?

I have got a Faultmate MSV2 so not familiar with the Hawkeye.
I have just looked at some of my old scans and the engine ECU scan, labelled EDC inputs, does not actually say "Boost Temperature".
It does however say "Air Temperature" instead which I assume is the same, just different terminology.
I remember reading on the Blackbox forum that the later diesel models all show -40 deg C air temp because the temperature compensation is built into the later MAF and the input is not used. Mine actually reads -38.88 deg C and never alters.
I think the diagnostic software from the factory was never tidied up when the later MAF was fitted.
Why it should show 124.8 deg? No idea.

If it's reading like any other NTC temperature sensor, a very low reading, often -40 degrees, means the sensor is open circuit and a very high reading means it is closed circuit. Maybe it defaults to 125 degrees when shorted?

Its also possible its just an unintended bug, and its reading something (or displaying something) that isn't really valid. I've known other vehicles to read voltages incorrectly (showing 17v when a multimeter will show its operating normally etc).

Is the hawkeye upto date as far as software is concerned? If its like the nanocom, it may be worth posting a query on their forum to get an answer. Otherwise try it on another diesel and see if it does the same thing if you have that option?