DOes the brand of O2 sensor really matter? I am usually one to put in the best where it counts, but saving a few bucks is always nice. I replaced my downstream O2 with a bosch unit(I am looking for an upstream O2 now), but I know NGK makes pretty quality stuff and the motorcraft lists as the cheapest on carparts.com. SO does any body have any insight as to what is the way to go here?