3-Inch Bellmouth Downpipe with Wideband Bung

The Tsudo 3 Inch Bellmouth Downpipe (20-1218-1) is engineered to enhance performance for Subaru WRX and STI vehicles. Constructed from durable T304 stainless steel, its cast iron bellmouth design is specifically crafted to reduce exhaust back pressure, leading to faster turbo spool and improved peak performance. The downpipe includes an extra wideband O2 bung for easy sensor integration. It requires reuse of the OEM bellmouth gasket. For installation on an OEM cat-back exhaust system, an adapter flange is necessary, which is available separately. While not strictly required, a professional tune is recommended to maximize the performance gains from this modification, as indicated by a user who achieved 291hp on the dyno with an intake, downpipe, and tune. Compatibility with Cobb maps is not guaranteed for catless downpipes. Fitment includes: 2008–2014 WRX (Manual Transmission only) 2008–2019 STI (Manual Transmission only) 2005–2009 Legacy GT (Manual Transmission only) 2005–2009 Outback XT (Manual Transmission only) 2009–2013 Forester XT (Manual Transmission only)