Compressing the air is only one source of intake charge heat.

Do you think heat conduction from the exhuast housing running 1000 C isn't going to conduct through the all metal housing to the ~80-100 C aluminum compressor housing? What about the turbine shaft? Those are two prime areas for extra heat to enter the intake charge through convection and conduction. Then there is friction added to the air from the compressor wheel which results from vigorously circulating the air.
Underhood temperatures are going to raise anyway since the turbo is under the hood. My statement that it may not heat the intake charge as much results from the logic that the exhaust has more time to cool down before it gets to the turbo so the turbine and housing will be cooler. Therefore the temperature difference between the exhaust and intake will be lower and the rate of heat transfer should be lower.
warmonger