How long have you owned the car? If it's unclear of whether those items were changed out recently or not, change them. Plugs won't make play a role in smog. It will be the O2 sensors amongst the items you listed. If there are no codes, you should be able to pass no problem.registration is due in a month and being sent to a test only. any pointers before i take her in?? miles at 17x,xxxmi's. thinking about doing plugs, o2 sensors and fuel filter.