[bepperb]

Yeah, O2 sensors, and anything else on exhaust manifolds for that matter, are a complete witch to get off. See if you can get an impact wrench. If you can't get an impact wrench, then get a breaker bar. If you can't get a breaker bar, improvise. (with a piece of cast iron pipe on the end of whatever you got)

Keep in mind you can get a cheap vom and "test" it without removing it, though. If worse comes to worst I can let you know what mine reads (04 I4).