They changed the rack because for some reason they decided to go with a wheel that has a different back spacing. You can go get an aftermarket 16" with the correct backspacing and not have this issue... you'll just have to go with a thinner wheel or it will stick out past the fenders.
As long as you keep the diameter of your tires to no more than 23.67" or less, by as much as 1/4 inch, there will be no problem with mpg. And your turning diamete will be same as OEM with 15" tires.