I haven't put in another bung for my wideband so I swap it out with the front 02 sensor different times. I have a new bosch narrowband sensor and at times it has given the code even when it is installed in the car. If you scan it, you can usually tell if its working or not, if the 02 is truly bad, it will sit steady around 430v or so. Sometimes just clearing the code a couple times will do the trick.

If the problem still occurs or if your pacesetters are leaking at the y-pipe, you can weld a new bung in the crossover pipe of the pacesetters near the rear head. The 02's should not vary much from bank to bank, especially not enough to throw off a narrowband.