Borla 08-14 Subaru STi / 11-14 WRX Catback ExhaustBorla Performance announces the release of a new quad exit Cat Back exhaust for the venerable 2008 ? ? 09 Subaru WRX STi. This race inspired system (PN140312) checks all the boxes on every Subaru enthusiasts? hit list, taking this flagship to an even higher realm, of performance. For starters, Borla engineers upgraded the STi? s exhaust plumbing from 2. 5 to 3" in diameter. The resulting increased airflow through the turbocharged powerplant provides