I am running a RamAir and TORS on my '13 R3T and I get about 27-30mpg. My tune has been tweaked on the dyno so I know it is about as good as it will get (tune and mileage). I am reasonably happy with the gas mileage because my truck and car get 14-16. My commute consists of about 6 miles of a secondary road, 6 miles of interstate and then another 6 miles of driving through town. I can't remember my mileage for road trips but I am sure if I putted along with the V2s it would be better than what I get when riding with another Rocket or 3.
One thing about my tune, the secondarys are not open 100% from the get go. IIRC they are at about 87% in 1st then open wide. I will look at the tune later when I get home to make sure.
bob