I want to say there is a cat on the 06-07 "header" with two O2 sensors One immediately before and after the cat. I dont think the second cat located next to the transmission has any O2 sensors associated with it. If that is indeed a cat at all. it looks like one. In my car i see in front of the engine located on the passenger side, the "header" has two O2 sensors before and after what looks like a cat. I dont see any other O2 sensors anywhere else. So if you get a borla it looks like you will need to get O2 sensor extenders to get to the cat section you will need from an 05 type cat which will be located near where your rear cat like thing is right now (next to the tranny). As for your question, i dont know how you could "gut" your cat without cutting your OEM "header" to get inside the cat with some type of cutting tool. Just get the borlas already.