I figured out, but that was the only diagram on vagcat.com. I couldn't find one showing the upstream ones, even though I skimmed through all the parts groups.

On my 1995 the upstream sensors are really easy to replace, as they can be seen toward the back of the engine (on both sides) as you lean over the engine bay.
I'm sorry nobody with Etka or the Ebahn manual posted a diagram for ya. My manual is for earlier year(s) models.

Good luck.

 

Im thinking about buying a factory service manual for my car...Where can i get a good one. Like the actual US manual for my car. 2001 Audi A6 4.2L

 

You you can order it directly from Bentley:
Audi A6, S6
1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
including Avant, allroad quattro, RS6
Repair Manual on DVD-ROM
ISBN-13: 978-0-8376-1257-7
W42 AC55 V030 CD
$ 99.95



You can also get it from
Arizona Autohaus Probably it is the best price around, although the edition may be older... That doesn't mean necessarily that is bad.
ISBN-13: 978 0-5376-1257-7
W42 AC55 V030 CD
$ 75.97

0r

Book Version; 1998-2004 A6,RS6,S6; OE Factory Authorized
$ 66.99

 

They are probably taxing you a high price for each O2S as well