a) They were a whole lot better than the denso pos plugs I had in there that gave me a misfire code anytime I idled longer than 3 minutes. It also smoothed the idle out and I got one heat range colder for the turbo. They have been fine so far, so my $25 was well spent.

b) I am wondering the same thing. I think they last as long as platinum plugs. :dunno: