I live in an enhanced area and the first time I had to take my Syncro in to
be smogged it did not pass. They were also unable to put it on the treadmill
because it is 4wd.  I took it to the one vanagon mechanic I trust to see if
he could make it pass.  He told me to take it back to be checked but make
sure the headlights are turned on and the a/c is on low.  I was skeptical but
I trusted this guy and sure enough it worked, I passed the second time.
Later the mechanic showed me this tip published in one of his trade journals
it was addressing vanagons specifically.
Loretta
87 Syncro GL
90 GL
82 Westy