I will try to provide direct links, but not sure if it will work properly.
Here is the 2006 Workshop manual:
http://www.gasgasmotos.es/rcs/enduro/ec_2006/manual_taller_eng.zip
If that link fails or you need more manuals...
Go to the main site -->
http://www.gasgasmotos.es
Click on "English".
Click on "Enduro".
Click on bike year (far right side).
Scroll down to bottom of page and download the desired manual.
Note: it appears they only have manuals for 2004 to 2007 bikes.
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For earlier model years, you can try GasGas Atlantic:
http://www.gasgasatlantic.com/tech.htm
Scroll down and you will find manuals for 2003 to 2006 bikes.
It looks like the 2006 workshop manual is also available here.
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By the way, I have the 2001/2002 owner manual (pdf format: 2.2MB) and the 2001 parts manual (pdf format: 10.7MB). They are too large to email, but I can ftp them to Jeff if he is willing to host them on this site.