You have a 4x4, therefore it actually has 4 cats, unlike the 4x2 which has 2 cats and 2 resonators. (this is AFAIK, as was the case on 06 and earlier Titans.) You can still remove the second set of cats and replace with a constant radius resonator, this is what I did. Complete removal of the cats/resos leads to popping and crackling (doesn't sound to good.) The portion you'd be dealing with is located between the headers and the "cat-back" portion, commonly known as the "B pipe." Try searching for "reso delete" for more info.