https://parts.subaru.com/
Select BRZ in the same model year as your current car (doesn't matter if you own a Scion/Toyota)
Click on "Engine and Cooling" Parts.
Look at diagrams for "Exhaust"
Call/visit nearest Subaru Dealership Parts Desk, or via online parts counter, or via online 3rd party Subaru parts store (which in the end are are usually run by dealerships anyway)
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Currently the Toyota corporate parts website is pretty cruddy, so it's pretty much impossible to access the diagrams there at the moment