i have a 2000 silverado and i decided to check my air filter......assuming it was gonna be a paper one. i pull the cover and what do i find.....this big oily black sponge. i think to myself tyhis can't be stock....but you never know. i'm thinking this is an aftermarket re-useable filter, and if it is, the guy who had it before went nuts with the oil because there is a puddle in bottom of the box. what do u guys think.