Any combination of 3" dp/test pipe with a COBB cat back. I haven't gotten pulled over in 2 yrs with this setup and Massachusetts state cops have a hard on for modified exhaust systems.

 

I like my Litespec exhaust

http://www.lite-spec.com/collection/evoixtione.html

Sounds great, not too loud but howls when your on it. Weighs as much as a very light thing and is beautifully made. You can get a really good price on one too if you keep an eye out, think I paid about $400 for mine on special.

 

People keep recommending the cobb but you can't get them new and they are very rare second hand from what I've heard.