Injen are 2.75" and neck down at the MAF. 2.75" is 70mm; the same size as the EPS TB's. The bottleneck is the stock manifold inlet. It's 60mm. You need to open that up and the maximum you can port it out is 64mm; which happens to be about 2.5". Looking at the Tim Bell Throttlebodies, they aren't running oversized ones either. They look stock, and they made 450+bhp according to their sale page. I'm hesitant to believe there is some sort of magic in the Admin intake or EPS throttle-bodies that make any more measurable power than ported stocks and 2.5" CAI's.
2015 Nissan NISMO 370Z GS IMSA CTSCC W/ Spares! for Sale in MOORESVILLE, NC | RacingJunk Classifieds