Audi TT MK1 - Large Bore Downpipe with Catalyst Delete (For 225 Race System Only)(Possible clearance issues on roadster due to additional bracing ) Milltek Sport Large Bore Downpipes are perfect when looking to improve both performance and sound. These downpipes are fabricated with a larger diameter than standard OEM parts, meaning that there is significantly more space for more gas to exit the engine and pass through, increasing efficiency. Used with our Catalyst Bypass Pipe, you can expect significant power gain without any