Di Filippo has a new website.. try
www.dpe.net.au
As for exhaust systems all after market systems are over the 90db.. they all seem to fail. we have helped a few customers pass EPA over the years with all types of exhaust.
With variable mufflers the cops are on to these mufflers. if they hear your car loud and then you switch it over your still going to get a EPA so I don't see how it will help..
Generally if you stay away from the hoon hangouts or spirited driving in populated areas you should have no problem.
Give me a call if you want to discuss this more