Are the Iridiums worth the extra money? They are supposed to be lifetime plugs, aren't they?
And for the other two responses,
Are the SP-515s worth the spark on my lil 2v 4.6? I know they recommended them for the 5.4, but they are two piece and I'm a little leery of that, even though I know my engine doesn't have the plug issues the 5.4 suffered....