I searched youtube for "mule gargling marbles". This is what I got:

https://www.youtube.com/watch?v=wtX-o7IyvNI

I don't think that's what the OP's car sounds like.

Straight piping will get you some more noise and maybe a little quicker turbo spool up. I've been considering straight piping mine just for the sound, but I haven't gotten around to it yet.

We have a performance sub forum here for hot rodding the diesels. I'm sure this has been covered there. As for me, when I want to go fast, I just ride my motorcycle.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.