Is the Powerboost the 3.5 Ecoboost with a hybrid system or is it a stepped down 3.5 with one or no turbos?

 

It is the twin turbo ecoboost 3.5 mated to a hybrid motor.

 

The Powerboost system does use pretty much the same 3.5L Ecoboost engine but also has a battery pack that runs an electric motor that is integrated with the specific 10 speed transmission. This combination frequently shuts the engine off when coming to a stop or even in slow traffic where it can run on electric only for short periods. I can often make the final turn into my neighborhood where slowing for the turn shuts off the gas motor, and run on electric about 1/8 mile to my house and up my driveway. I've also had times where if the road is very flat or with a slight down hill that the gas engine has shut off and run on electric up to 52 MPH at a steady speed for a bit. That is one of the tricks that it uses to increase the fuel mileage over the standard Ecoboost.