If your code reader indicated that the 02 sensor that was out of spec was "Bank 1" I believe that is the passenger side exhaust path, cylinders 1-3. You could try swapping sensors on that side and see if it helps.
http://mike.focke.googlepages.com/whatcylinderiswhere%3F
I would still recommend replacing all the 02 sensors for new OEM ones though. Think of it as being similar to only replacing one spark plug - might help a bit, but not as reliable as replacing all at the same time.
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