Yup. Models with those actually have three catalytic converters: the two in the manifold and a normal one in the pipe under the passenger seat. O2 sensors are installed before and after the small ones in the manifold.

Might read this thread for more information on the O2s: https://www.cherokeeforum.com/f2/o2-sensors-159102/

Generally there are a lot of reasons that fuel economy can be so bad. If you want to check your cat's operations, you need an IR thermometer (aka temperature gun, usually have a red LED or laser sight). Outlet temperature should be higher than inlet temperature on a working catalytic converter, and once warmed up you shouldn't notice any smell if you stand near your exhaust (I don't recommend sticking your face up the tailpipe unless you don't mind a bit of brain damage and asphyxiation)

 

like Salad said, or bite the bullet and take it to heep dealer and have-em scan it, replacing the cat for a 2000 is whut 8-900.00?