Its going to be big time loud when you get your headers and cats.
I'm also suprised by how much the stock mufflers quiet down the L99. I've got the GMPP "off road" version axle back on my car and its louder than I thought it would be. When I add long tubes its going to be real loud.
The L99 mufflers are different than the LS3 mufflers. They look the same, but when you cut them open the L99's is more restrictive and has more packing.
2010 Camaro 2SS/RS, L99 A6
Bolt ons (12.10 @ 113.60 mph, 1.77 sec 60')