I don't think there's much info here for diesel because there's not much real benefits. I changed my stock exhaust from axel-back with a straight 2.5inch pipe. It does add a deep drum sound to my car and it does feel like it's bit torque-ier at lower rpm. However, you should be careful doing exhaust for these light duty diesel cars, if you want do exhaust system for better sound, be ready to spend big because you would need to change everything from turbo-back to get something decent. Anything from cat-back doesn't change as much as a petrol car because I think the sound gets muted somewhere from turbo-back. Also, you need to do lot of research and find a reliable person/company replacing your exhaust system to have very good guarantees and has knowledgeable experience with your car. If you're after performance, the amount of money out of your pocket is not worth it because you would only get a tiny bit of increased. Diesel engines are built to be efficient, any changes to it could easily compromise not only the performance but also the lifetime of your car. I'm no expert so I could be wrong. But in Australia, no one really wants to touch diesel.
