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'91 200 TQW K&N Filter

I'll try sending this without subscribing.

I thought I'd pass on some information derived from using a K&N filter in a
'91 200 TQ Avant, factory serviced for about a year and a half in partially
dusty conditions.

As I am always checking under the hood for things to do, I removed the K&N
filter cartridge a couple of weeks ago after installing it approximately
6000 miles ago.  I realize that it is advertised to go 40,000 miles between
servicing, but again, I'm always checking such things.

I found several bugs, and some dust/dirt piled up on the windward direction
of the pleats, but the other sides were mostly the original pink where not
much dirt had been trapped. The element was still oil damp. Normal.

But upon examining the Air Mass Sensor bore, there was a layer of fine dust
all around the inside.  Further snooping revealed dust piled up on the
upstream side of the pleats of the hose that goes to the turbo!  Not a
welcome sight.  Now the element is NOT dirty enough to clean, and my
experience with K&N filters is that they get better as they get dirty anyway
(I used to sell a lot of these things to motorcycle racers as a dealer).  I
deliberately examined the Air Mass sensor bore before installing the K&N to
see if the stock filter passed any visable dirt, but it was clean.

Needless to say, I zipped down to the local Checker parts store where they
happened to have a Fram filter the right size.  A very well made item from
Italy much more carefully built than the original Audi paper replacement
removed for the K&N.  In fact, the Audi filter's pleats were so closely
packed and distorted that a large center area of each pleat had moved up
against its neighbor far enough to limit the useful breathing area down to
about 50% of the intended surface area. For an engine that passes a lot of
air at full boost, this is not good.

I welcome any comments about the K&N, but I'm not using it again.  Further,
I won't buy an OEM Audi replacement either unless I examine it thoroughly first.
Since the Fram replacement was $15 I'll probably stick to it.