It is located at the bottom left of your engine on your accessory belt(looking from the front). The main reason to remove is just to clean up your engine bay. It also reduces about 20lbs. I think i got a little better gas milage after i removed mine too. Hope this helps....
you might try researching it a bit more before you go pulling it. The smog pump puts air in the cats to help mix w/ the exhaust to make it easier on the cats (basically). If you have cats and you delete the smog (air) pump, you're gonna screw your cats up...eventually. That's the general idea anyway. I'm almost positive Michael Yount had a very good and detailed post on this, so maybe try running a search for smog w/ Michael Yount as the poster.
i thought the pupose was to pull the exhaust gas up through the engine. this would also involve the egr...or so it was explained to me. also if that were the facts, what about the front two cats, mine had four as i think his would to. however i have been wrong before. are you in a smog controlled area, if not ditch the cats and it wont matter.