Well of course just mufflers isnt gonna make any noise but almost stock noise..... Best bet is to get a cat back system... OR you can just redo the piping to 2.5 inches after the catalytic converter... and remove the resonator.... You should be able to pass smog since the Sensor should be in front of the converter... Should be a big sound difference after and a little hp gain... all n all good luck with that...

FYI anything over 2.5 inches would probably loose back pressure and overall HP... not really worth it...