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Since I have a LH 2.4 , I wasn't aware of this procedure, but I found it here. The way I see it, it is only meant to account for different responses between different AMMs. So basically a set and forget thing, and preferably done with a CO analyzer.
I'd say the best way to check if the AMM needs readjusting at these cooler temps but with the preheat hose connected is to perform the calibration again and see if it is now out of spec. That's the only way to answer your question with certainty. But of course step one is to make sure the thermostat works correctly.
It doesn't really matter that the air density changes AFTER it has passed the AMM, provided that the whole inlet tract is not leaking.
Yes, the mass of the air changes with temperature, altitude and moisture content at ambient pressure. But once it is inside the inlet tract, that AMOUNT is known and no subsequent cooling or heating or compressing it is going to change that amount.
The turbocharger compresses the air going into the cylinders, but that simply means that upstream more air must be drawn in when compared to a NA engine, which is, of course, accounted for by the AMM.
Compressing air makes it warmer and thus less dense. Exactly what you don't want in an engine, so the intercooler takes away that heat again.
The ECU tries to keep the hot wire temp constant. That means combatting the cooling effect the passing air provides. More cooling means more effort and that's what the ECU derives the amount of air entering the engine from. Very little effort no load (only ignition on) ~1.4 V, ~2.3 V idle and increasing to 5 V full load at high revs.
Edit: the ECT tells the ECU whether the engine is warming up. When cold, the ECU enriches the mix to account for condensation of fuel on the cold inlet manifold etc. Basically what in the distant past we used to do manually with the choke. It only tells the ECU about the engine coolant temperature. I don't think the ECU cares much about it above a certain temperature.
The O2 sensor closes the loop. This tells the ECU whether the mix was right, and the ECU corrects accordingly.
But there seems to be confusion about your engine having a turbo. It says here that only non turbo engines have the airbox thermostat.
So that has me wondering, what is the Bosch number on your ECU?
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