Actually Brent, we are.

If someone wanted to put on the extra cat later on downstream in the system, and wire in the sensors, then it would be perfectly legal.

Yes, you would need to put in an O2 sensor bung about the same place as the one shown in the picture above to get the rear O2 sensors to read correctly.

Nissans don't like the O2 sensor simulators, as Nissan has a logic built into the programming that the sims can't duplicate. What happens when the sims are acting like the vehicle is fully warmed up and it's still on cold idle? The computer throws a code. Or when the evap system decides to purge and the cats react to it? Sims can't and won't duplicate the real thing.

We've seen so many sims on the SpecV Sentras and 3.5 Alty's fail to correctly simulate that it's not even funny any more.