[YellowCobra04]

I just bought a used Bassani catted x-pipe off a wrecked 2003 cobra and when I got it there was only 3 O2 sensor holes. Ther are the two behind each of the cats and one on the driver side where it bolts to the exhaust manifold. But my problem is I dont have one on the passenger side at all. The thing I don't understand is why there is only three, and how the guy that first owned it before me ran it. Thanks for all the help.