I had the stock muffler swapped for a glasspack. I don't know the exact type (although I do think it's made by Thrush), but it was an almost perfect bolt-in replacement for the stock L03 muffler. I left the cat and resonator in place (for now).
The glasspack has notches inside the pipe which are supposed to make the exhaust gas swirl and improve the sound
It sounds almost the same as before at idle, but gives a nice low rumble at part throttle, and a loud rumble at full throttle. It's almost like there's a guy with a really big drum in the trunk
The glasspack cost about $100, and about another $35 to install.
I'm happy with it, it's not too loud which is important since it's my daily driver.
I want to delete the cat but I'm afraid it'll get annoyingly loud. Does anyone have experience with this?
PS Thanks go to Maikel for giving me this idea. A lot cheaper than the custom exhaust I was about to buy!