If you have to pass emission testing its going to be next to impossible.
From my experience if you don't want it to sound nasty with a gutted cat, the best thing is to pull the cat off and cut it open then clean it out and cut a length of piping to fit inside it and weld it back up. This prevents it from sounding really bad from just a hollow cat and also allows you to still have it appear as if a cat is installed.
If its not required to have a cat, don't gut one out simply remove it and replace it with pipe.
"Time you enjoy wasting, was not wasted"- John Lennon
"The Jeep is a manly device. And a womanly device. An American device. Itís a fitting instrument to transport the free people of a free nation with the respect to which we are entitled and the dignity that we deserve. Okay, weíre a little crazy to have a Jeep for a daily driver. But if we go off our meds, we might wind up in a Prius"-P.J.O'rourke