It definitely sounds like you may have the wrong O2 sensors or have them switched around. I was lucky enough to be able to pull my 4.0 and label everything as well as I only have one upstream and one down stream.
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Herc.Custom Green paint. RC 4". 5 Goodyear 33X12.5 MT/R w/Kev. Cragar V5's. Corbeau Moab seats. Optima Yellow.XRC8 Comp Winch. XJ 4.0/AX15
WTT: 4" springs for 6"
WTS: 4.2 parts. Fuel lines, pump, block, head, accessories, just ask