Hi Mark.  I had the same problem when I was enquiring about this.  I 
currently have a the Syncro Special filter installed... had it for 3 
years now, and it's still clean!!  The dirt trap prior to the filter 
box does a good job of getting rid of most of the dirt before it hits 
the air filter.

Up here, a Syncro filter is $134 CDN, versus about $40 for the 
regular filter.  Both will work.  My dealer doesn't even stock the 
Syncro filters as they use the regular filter in the Syncro.  A 
Syncro filter could last up to 5 years.  The Syncro filter is useful 
if you are in extreme dust conditions.

Hope this helps
Harry.

> I just learned that there are two varieties of air filters available for my 
> '87 syncro. The standard filter is round and costs about $11. Then there is 
> a heavy duty model for dusty environments that costs $68. It is oval 
> shaped. Both filters fit in the same housing. Do any of you off-roaders use 
> the expensive dusty-environment air filter? Seems pretty hard to justify 
> the 6X cost factor over the standard filter.
> 
> Mark McCulley
> '87 syncro Westfalia
> 
> 
> 
----------------------------------------------------------
Burnaby, British Columbia CANADA
'90 Syncro Westfalia  email: hyates@bcit.bc.ca
'87 Golf Diesel       WWW:   http://www.bcit.bc.ca/~hyates