In NSW, there is vehicle noise and stereo noise.

Look here:

http://www.epa.nsw.gov.au/noise/vehiclenoise.htm

Please note that in NSW if you sell a registered vehicle with a loud exhaust, you can be fined up to $400 for selling the vehicle.

If your car is smoking.. you must fix it, unless it's a diesel. $$ have nothing to do with it. Cops would be policing emissions laws as the reason.

The Tasmanian Transport website is almost empty with information, so I don't know how much of the NSW regulations are relevant for you.

Chris