I know of some people that keep their stock stuff around too, and just switch them out when they have to get inspections, such as the air box and resonator.
someone receltnly posted that they needed those parts....just for that purpose as they had thrown out thier old ones b4 moving to CA. Ill be getting rid of my resonator, and modify the air box...but I have no inspections up here to worry about. But will keep around if I ever sell and want to keep those parts ( mod parts) for next project. So keep your old resonator around and if you ever come across a cheap stock air box, might be worth getting and keeping on a shelf. Maybe talk to other california 4runner owners about that.
glad you know not to over oil the filters