But it also uses start/stop technology and active shutters in the grill (not sure if all the new engines do or just it).

As far as EPA tests for the eco, yes it will get into boost unless you drive with an egg under your foot and on flat land. More boost= more power= more fuel burned.

 

The 3.5 has a different tune, even without the turbos spinning.

More HP = more fuel used. Period.

Even 2 of the same engine can get different efficiency scores. Case in point, the 2.0 in the Escort and early Focus vs the Mazda 3 cousin using the same engine (Mazda having a more aggressive tune)