I found an interesting site on various technical aspects of automobiles,
possibly of interest to those repairing or modifying their vehicles. Some of
the articles are VW specific, others of general interest. The web site is
geared for repair shops, rather than the home enthusiast. The index page
(3rd link listed) is a good way to access the articles at the babcox site,
and interesting others.

See:
http://www.babcox.com/ic/

and:
http://www.babcox.com/tr

The author of many of the articles has created an index of the articles at
the babcox site, and further reading, at:
http://members.aol.com/carpix256/library/index.html

In particular, if your car failed emissions testing, check out:
http://www.babcox.com/ic/ic39768.htm

Interested in Bosch Platinum +4 four-electrode plugs?:
http://www.babcox.com/tr/tr119832.htm

Enjoy!

ron antaki