Also known as the "reso delete".

There are two resonators on the stock exahust on the 2WD titans. They are bolted to the stock converters (downstream) and then bolt to the y-pipe. They are double walled and are only about 1.5" in internal diameter. Some people are running straight 2.5 or 3" pipes in their place. Others (like me) are running performance mufflers instead to help a little with the noise.

The 4x4 titans come with secondary cats (I don't know why) but you could do the same mod as the 2WD models since those mid pipes are the exact same dimensions.

With the reso delete on my titan I got a 0.15 sec gain in the 1/4, but already had the Banks in place.