+1
The precious metal plugs are about one thing… longevity. All the car manufactures got in on the “100k miles without a tuneup” crap. Part of being able to do that was having a plug that would last 100k, and that’s why we all have these fancy plugs now. What they don’t tell you is a simple copper plug will actually work better if you change them every 20k or so. There was a huge thread about this over at ls1gto.com, with lots of people talking about how much better their cars idled after switching to NGK TR55’s. I had my doubts, but going from my 86 Fiero that I worked on constantly to the GTO I was having “wrench turning withdrawl” one weekend and decided to swap them out. Sure enough, they really do work better, and my car only had 5k on it.