BBK Hi Flow direct replacement 2011-13 Mustang V6 X-pipes offer improved performance and feature 2-1/2″ Tubing with a merged X to maximize the potential of Ford’s 3.7L V6 engine. They are a direct fit to factory stock headers and aftermarket shorty exhaust headers including the new BBK CNC series headers for the new V6 Mustang. They feature factory OEM O2 sensor locations and factory style die-stamped flanges to ensure a perfect fit and BBK In-house dyno-testing has shown solid horsepower and torque gains, depending on application. All BBK full length X pipes are designed as direct bolt on to factory headers or any aftermarket shorty headers as well as, of course, BBK shorty headers for weekend track or race use the off road version works well – but for stree we only recommend the Full X pipe with 49 state legal converters. BBK Performance X pipes have been the number one performance brand Ford Mustang enthusiasts have enjoyed for years. Each BBK X pipe offers performance, quality and value that guarantees years of top performance for your Ford Mustang. Please note: BBK Performance and ALL authorized Distributors – CANNOT SELL THIS PART TO ANY END USER WITHIN THE STATE OF CALIFORNIA. THIS PART CANNOT BE SOLD OR INSTALLED ON ANY POLLUTION CONTROLLED VEHICLES IN THE STATE OF CALIFORNIA. OFF ROAD pipes do not have any catalytic converters and are manufactured and represented ONLY for the purpose of OFF ROAD-RACE USE ONLY in some cases they will require a tuner to switch off rear O2 sensors.