my car failed with high hc(ppm) standard 157 my reading is 357 and high co(%) standard 0.97 my reading is 3.83 ..........does anybody know what could bring my numbers down in a big way? i know it could be the EGR valve or co2 sensor or the catillac convertor but that is my problem it could be so many things SO WHATS THE MOR LIKELY THING THAT I SHOULD START WITH?