http://www.knfilters.com/wraps.htm
anyone have experience with these?

I run a K&N Pre-filter on my ZZ502, shown HERE (http://www.72chevelless.com/082802-02.jpg). Keeps a lot of dust out of the filter, and is cheap insurance.

is that the one made of foam?
or the one made of polyester?

do you drive in very dusty areas? wouldn't think you would drive that (very nice by the way) on dirt and gravel roads.

My pre-filter is the one made out of poly....a very thin "fabric" of sorts with an elastic band around the edges for a nice tight fit on the filter. No, I don't drive the car on dirt roads, in fact I live 5 miles down a dirt road and never bring my Chevelles home. Luckily, I own a plane & hangar where the toys get parked. Just understand that these filter wraps will intercept a bit of airborne dust before it gets sucked into the pleats of the filter. You'll be washing the filter less and giving it even more longevity.