Well - in my 1998 there are actually three of those 3 x 10 filters that slide together to make up one larger 9 x 10 filter that covers the evaporator. I did find that the bottom one - which is the one you pulled out - is the dirtiest.
Did you buy a new one? Check out this page -
http://www.autozone.com/autozone/parts/Cabin-Air-Filter/_/N-8gdaf?filterByKeyWord=cabin+air+filter&fromString=search - does the bottom section look like yours?
I hate to be the bearer of bad news but I'm guessing that the other two are still up above in the evap box. Mine slid down fairly easily once the one below was out. You have to remove each one of the three sections one at a time.
Don't buy the Fram filter - piece of crap from China fell apart within two seconds of trying to get that sucker in there.
If you wind up wanting to replace the other two sections let me know - there are a couple of tricks to make the process way more painless.
I think one of the other guys said that the NAPA part was a good one -
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Cabin-Air-Filter/_/R-FIL4874_0066957339
PS Make sure you note how it looks when you're pulling the other two sections out - once you've got them out it gets a little backwards on putting the new ones in - just remember that the tabs go on top and the grove goes on the bottom and the flip out pieces go toward the opening.
Another note - after you get them all out get your shopvac out and put it up to the opening where the filters came out - I had a mess of leaves and dust up in there. I actually went underneath the hood and took off my wipers, the screen covering the area below, and vacuumed down there as well - it's supposed to clean out when it rains through a couple of rubber drain flaps on each side under the screen but when you get too many leaves and you start going down the road at 70 mph I guess anything in that area can be blown around and wind up in the evap box.
I even drove around on the highway a couple of days without the new filters in yet just to let the wind help push any remaining dirt/debris out the open access panel on the inside. Probably overkill - but I feel better knowing it's really clean.
