aFe Large Bore-HD 2-1/2in SS Cat-Back Exhaust | VW Jetta TDI (11-12) (49-46401)Large Bore HD 409 SS Cat Back Exhaust System with Dual Rear Exit by aFe. Exhaust System Type: Cat Back. Exhaust Tubing Material: 409 SS. Main Tubing Diameter: 2. 5". Exhaust System Sound: Aggressive Loud. Get increased exhaust flow, more horsepower and torque, improved performance and lower exhaust gas temperatures with the aFe Large Bore HD Cat Back Exhaust System. aFe dyno tests every system for maximum gains, and constructs them from mandrel bent