If the hose is long enough you can try to pass it through the rubber gromet together with the electrical wires behind the glovebox, otherwise choose another factory installed wire or cable (such as the throttle) that goes through the firewall and see if you can squeeze the hose through the same hole. If you can not, then drill a small hole next to the one that the wire or cable you selected goes through. When you are done get some silicon and spread it around the hole that you drilled (after you pass the hose through, of course) so that you can seal out any water from entering the interior. Do not drill through the floor because it consists of two layers spaced about 3 inches apart.