I worded that wrong, my mechanic doesn't just think it's the plugs; he suggests to have them changed as part of regular tune-up, but doesn't think it's going to fix the issue of the different codes that are coming up. I trust my mechanic (a rare occurrence I know!!) and if he wanted to waste my time and money I would be shocked! He has already had my car in the shop and checked the codes on 4 separate occasions now and has not charged me for any of it, even after I asked him what I owed him repeatedly; I was told it's on him!