Here is a plug for the HD Syncro airfilters:

I suspected my aging engine was loosing power.  It occured to me the
airfilter may be restricted, but I had recently replaced it.  So I
considered other possibilities (since I started this site subscription
to v@g, there seem to be so many possibilities as to why one could loose
power ).  I use this vehicle when I go on trips, so it does not get
driven regularly.  Finally, I took a few moments to take the cover off
the motor and take a peek.  Seems a critter had made a nice home in
there over the winter and placed some building insulation in there to
make things cozy.  The filter element was a Mann brand with VW part
nubers and German writings (stock paper element I suppose).  I was a bit
unnerved by the critters desire to chew some parts of the paper element
creating a few holes in the filter.  Thankfully, I had recently
purchased an HD syncro airfilter from a vendor who is active on this
site.  This filter is what it says, heavy duty.  The metal grids should
protect the element from any future rodent encampents, but I am
considering a cat to keep watch on things.

I did wonder what that clear (now) catchment thing was upstream of the
airfilter.  Is it part of some sort of gravel-catcher or cyclone system
designed to "prefilter" the incoming air?

Keep an eye on those air filters!

Ray
90 syncro westy