Hey darren.
Reasearch a bit about varex mufflers, type it into youtube, that might be what your looking for.
Remote controlled exhaust, when flap is closed, its factory quiet, when flap is opened, its loud and you get the performance out of it.
Altho not legal, but it will still save you lots of headaches if you know what i mean. Keep the neighbours and misses happy too which is a plus.
approx $400 plus installation.