There recently was a thread regarding poor running of a Vanagon after a tune up.  I read the conclusions and don't think it covers my problem although It is related...
I just installed a new O2 sensor.  It was a Bosch which needed to be spliced in.  I know how to solder and made some fine connections which were covered with shrink wrap afterwards.  Anyway,  it's now running really crappy...Smoke, black tail pipe, sounds like it's missing....the works.  It did run fine before the switch AND I unplugged the O2 sensor and went for a test and it ....dare I say, ran great.   Whats Up?