I have had an occasional hard miss in my chev P.U> for about 5 years. Have brought it to many "Professional" mechanics, in Washington, Canada and Alaska. While spending a few thousand dollars, the problem was never fixed, nor even correctly diagnosed. This includes mechanics at two separate chev dealerships.. Upon bringing it into the folks at Edmonds...…….while they could not duplicate the miss, they correctly diagnosed the problem and corrected same. Its a great relief to me. Thanks guys!