the sensors were Bosch, $80 ea. Supposedly they make a generic sensor and a specific one. I, of course, chose the specific (more exspensive) sensor.
The gunk on the front sensor was there from before. I've had the valve cover replaced recently. But when I saw the two, the front was definately gunk upped and the rear was nice and clean. I definately support my mechanics theory based on what I saw... ($.02)
