i have a slp cat back exhaust and it isnt loud enother for my likings. i would like to make a cutout like the borla setup. has anyone done this before. is it easy to have a muffler shop do it

 

Somebody on one of the fourthgen boards or somewhere made a setup kind of similar to what you are talking about. It used a small diameter pipe (maybe 1") to partially bypass the muffler. It linked the muffler inlet pipe directly to the passenger side tailpipe. I don't remember which board I saw it on, but I believe it was written up as a tech article.

Edit: I got bored and found it: http://www.ls1.com/index_ls1_mods.html
Just click on the link and then pick "exhaust mod"

Not exactly what you had in mind, but it's all I've got.