Nissan must have studied BRP's(Bombardier Recreational Products) book on fuel delivery....
In their snowmobiles, they have used the same technology for years, they called it "SDI" or Semi-Direct Injection, where they used an injector in each throttle body and another two injectors in the base of the engine, near the ports. Lately, they have been starting to use direct injection directly into each cylinder(minus the throttle body injector), borrowed from the line of Evinrude and Johnson outboards that they produce, this one is called "E-Tec".