Well I did not notice any dust on the inside of the air box or in the tube leading to the engine. Did a white glove test.

Of course this does not mean anything. The filter was very dirty and had bugs in it!!

I ended up replacing it with a Purolator. It seems like I lost some peppiness but this might just be psychological as all the reading I have done points to the fact that cotton gauze filters are only a little less restricting than "paper."

The last item I read was:
http://www.bobistheoilguy.com/airfilter/airtest1.htm

Mike