you need more than JUST the CAI. a tuner plus an aftermarket muffler will also help.
i had a 2008 armada prior to the 2012 Q, i had a magnaflow muffler, a bully dog tuner and a injen CAI. i definitely noticed HP gains, less restriction when accelerating, and improved MPG.
just on the Q, i removed the stock muff and resonator and installed a magnaflow muffler. i also use 100octane petrol. those two have given me improved acceleration and MPG. i get 14.5 MPG highway. the Q is 4X4 all options.
point is you need more than JUST the CAI to get better MPG....