Does the trip meter read gas mileage accurately with engine mods?

[red01vr6]

I always wondered, especially if I supercharged or turbocharged my car, if my mileage on the computer in the instrument cluster would still be giving me accurate readings.
Supercharger, turbocharger, bigger injectors, ecu tuning, even basic airflow mods (i/h/e w/e)... these all obviously affect your gas mileage... so does the computer adjust?
Even if the mileage is read by throttle input (or however it's read)... there's still a dramatic difference.

[red01vr6]

Really? No one knows? >.<

[FigureFive]

My only mods are intake and UM tune. Since getting the tune the mpg seems to be off slightly. When I divide the miles driven by the gallons added it comes up 1-2 mpg less than what shows on the MFA.