I have NGK iridiums in my car, and a slight miss. An annoying but slight miss. Perhaps it is related to the NGKs
But I'm confused (whats new?). What kind of life expectancy is there on spark plugs in a sup? My altima has 60k on it running factory plugs. I know the sup is a turbo, runs hotter, blah blah blah, but changing plugs every 5k seems a little extreme.
I don't know how old my NGKs are, they were in the car when I bought it. One was checked, and it looked clean. But, perhaps there are other indications that the plugs are going bad..?