Hi, i have 99 accord lx with95 k. CEL has been on awhile and finally got code reader and that's the codes that it gave. Which 1 is the most important/ critical? Ive smelled rotten eggs when ive backed up in my driveway for years. Does that mean the cat. ? Everyone i know says yes but could the EGR,intake,or O2 sensors cause that ? Where do i start? Any help will b appreciated !