Ford changed the diameter of the factory piping after 2010. If you're running a 2.5" aftermarket mid pipe, then you can definitely run this set up!
I would recommend giving the manufacture a call and they'll definitely be able to help you out! You can also give my Customer Service team a call with any questions. Our Mustang Experts are here Monday-Friday from 9AM-9PM EST and Saturdays from 9AM-5:30PM EST. If you want to hit them up, their number is 866.727.1266.