What gave you the idea the sound was magnified 100x? I had a non resonated system fitted to an Octavia, which on a petrol would of been OTT. However on a diesel it barely made a difference (something I found from research, I wouldn't of had one if not.). From what I read you really need a straight through pipe, which would make some noise (all be it terrible). Performance is easy to gain on turbo diesels, with a good map you can gain MPG and power. Not sure what other "performance" mods are done on the diesels generally, but I think the remapping is great.
The 3.0l Audi diesels engines can sound reasonable with the right system on IMO :blush: