The CTS B6 A4 1.8T High Flow Cat Pipe is the premier cat pipe for your Audi.nnOur high-flow cat is designed to seamlessly fit in place of your restrictive stock catalytic converter, which is situated immediately after the turbocharger. Our high-flow cat 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 our high-flow cat. 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 high-flow cat. In addition to being one of the best bang for the buck performance upgrades for A4 owners, our cat pipe is also a very attractive piece. Each 3″ high-flow cat 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.nnFitment:nn2002 – 2005 B6 Audi A4 1.8TnnProduct Details:nT304 stainless steel constructionnMandrel-bent stainless steelnFully tig welded designnOptional third 02 bungnInstall hardware includednGreat power upgradennTo remove the CEL that will occur, proper tuning software must be used. The use of stage 2 software upgrade is strongly recommended.