I wanted to hear the v6 a bit more so have had both rear boxes cut out and a straight piece of pipe put back in and retained rs tailpipes so it looks standard. There is a youtube video showing a red a6 3.0tdi with this delete and they reckoned 20 bhp gain due to being very restrictive. I don't know about that but wanted to share the outcome as it was a bit of an experiment. My car already has gutted dpf, cat still in place and rear boxes removed . A slightly deeper tickover, does roar a bit more and you can here turbo spoiling up and without doubt it pulls harder which surprised me. Look forward to warm weather and putting the roof down. It was a cheap way of getting more growl. The a5 3.0tdi seems to give a nicer noise if you search youtube but I don't know if that's a full system with larger diameter piping but its not much louder, pulls harder and sounds more meaty without sounding 'carlos'. Am I mad, I hope so!