Injen Technology has examined the stock down-pipe and found prominent potential on improving the OE design by using mandrel bent stainless steel for optimum flow and corrosion resistance. TIG-welded by hand for race proven durability and endurance and eliminating any possibility of cracking during heat cycles. All of the Injen downpipes are uniquely designed to increase exhaust velocity for improved horsepower and torque. Just like all of our other performance parts, we dyno test our Down Pipes in-house and proudly build them in Pomona, CA. Performance Down-Pipe with CAT, Part No. SES1205DP, 2008-2014 Subaru Impreza WRX STI H4-2.5L Turbo, 2015-2020 Subaru WRX STI H4-2.5L Turbo, 2008-2014 Subaru Impreza WRX H4-2.5L Turbo. Downpipe; w/ Divided Wastegate Discharge; w/ High Flow Catayltic Converter Subaru 2008-14 WRX 2.5L Turbo; 2008-14Sti 2.5L Turbo Downpipe w/divided wastegate discharge/high flow catalytic converter