CTS Turbo’s test pipe is designed to seamlessly fit in place of your restrictive stock catalytic converter, which is situated immediately after the turbocharger. Their test pipe features 3″ stainless steel piping, smooth mandrel bends, two 02 sensor bungs with an option for a third. Substantial power gains, improved exhaust flow, and a more throaty sound are the main benefits of installing their test pipe. Upon inspection, you will notice a flare which is nearly 4″ this flare then tapers to 3″ and is designed to allow for optimal flow as the exhaust gas transitions from the turbocharger to the test pipe. In addition to being one of the best bang for the buck performance upgrades for A4 owners, Their cat pipe is also a very attractive piece. Each 3″ test pipe is mandrel-bent, hand tig welded. Do you need an additional 02 bung for data logging? Well, that’s no problem! Tig welding additional 02 bungs can be done for an additional charge.