They are difficult to find but the best filter upgrade for our 2.1L engines is the heavy duty version used in the Syncros. 025-129-620-B. This is a larger filter element which offers more air flow capacity when clean and can of course hold more dirt. The Syncros also get a cyclone type dust-water separator that seems to help a lot. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Loren Busch
Sent: Sunday, December 04, 2011 1:15 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Oil recommendations simplified

 RE: K&N Filters
Based on something I found on this (or another VW/Vanagon list) I went to a K&N filter several years ago in my '90 Westy. Because of the comments in the message above, based on hard data, I'm now having second thoughts.  So a quick Google search finds this:
<http://www.nicoclub.com/archives/kn-vs-oem-filter.html>
Again, hard data, not hype or anecdotal evidence.  I think the K&N is coming out (it's due for cleaning anyway) and I'm going back to the stock filters.
And I'm sure there will be a bunch of comments on this both ways, waiting for them.