A nice table at the bottom of this
page about exhaust size and the torque.
Given the fact that our 2012 FF is a CID 121 et le the best exhaust diameter for it seems to be 2"-1/4 or 2"-1/2.
Edit: changed the CID to 121. Because of the HP, I think the max for the exhaust of the FF would be 2.5"
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