Volvo Repair: oxygen sensors, oxygen sensors, wiring harnesses

Question
My 1997 850 volvo non-turbo showed a PO141 so I spliced in a universal sensor downstream.  Then I immediately got a 131.  So I spliced in a universal upstream. Unfortunately, the 131 keeps coming back. Suggestions?  I know that Volvo recommends changing both wiring harnesses when an O2 sensor is replaced on the 97. Should I do that?  Did I make a mistake in using the cheap universals?  

Answer
Steve, never put that garbage in there.  Its a nightmare.  Spend the extra money and get the real bosch sensor.  I dont know where you read about the harnesses.  Replace both sensors if you really want too.  We never replace the harnesses unless there is something wrong with them.  Roger