I did it in my Quad4 Pontiac years ago. I bought some 5" dryer ducting, sealed it against the enlarged opening in the airbox. It snaked around behind the bumper and fed off the backside of the grille. Didn't notice any driveability issues with rain or snow. The K&N caught quite a few bugs and I would need to get them off of it from time to time. I did notice a little better response on the freeway though.
I have been thinking about it for my car, but haven't done it yet.
