Map sensor question...

They don't measure manifold vacuum. Instead they measure ambient air pressure. You'll notice they don't have a hose going to the intake manifold like those on other N/A vehicles. These are called BAP (Barometric Air Pressure ) sensors rather than MAP (Manifold Air Pressure) sensors.
 
BAP sensors measure barometric pressure and by using one the system can accomodate changes in weather as well as altitude changes since both things influence barometric pressure.
 
Due to the fact that Naturally aspirated vehicles are... naturally aspirated, their manifold pressure levels can give insight into ambient air pressure.

Since the supercharged motor pressurizes the intake manifold in a way unrelated to external air pressure, measuring such doesn't really give any insight into ambient air pressure.
 
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