My '91 wouldn't pass the hydrocarbon test, but carbon monoxide was 
     okay.
     
     I found the car had sub-optimal plugs - they were okay, Bosch, in the 
     same relative heat range, but not exactly what was recommended.  
     Changed them and the numbers improved somewhat.
     
     Ended up at the dealer for the Fuel Injection recall which had never 
     be done.  Decided to have them diagnose the problem.  Ended up 
     replacing the cap, rotor, and plug wires.  I knew the wires were 
     aftermarket and had heard from other sources that this might be the 
     problem.  The cap and rotor were no big deal price wise, but the 
     dealer price on the wires was totally beyond reason.
     
     Still, the thing passed.
     
     I'm really beginning to believe what one list member said a few days 
     ago, namely that the wasserboxer needs to be treated like an aircraft 
     engine - don't cut corners.
     
     -Blaine