Depends on what model you have. For the V6, its 2 1/4" pipes with center inlet and offset outlet.
GT would be 2 1/2. Not 100 sure on inlet/outlet, but should be the same. (Just crawl under there and see where the pipes go in and tips come out)
No clue on ecoboost.
2015 Mustang V6. The 'Go' came from the factory. Working on the 'Show' part.
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