The 171 & 174 codes would be coming from the first set of O2s before the pre-cat. Did you remove these when you gutted your pre-cats? (Maybe they got damaged...) What's up with the 2 sets of MIL eliminators? Is one set just hanging there or did you also put some in for the first O2 sensors. ??? Try cleaning up your upper o2 sensors, and put in ONE set of properly connected MIL eliminators for the bottom sensors and see what happens. You may need new upper 02 sensors.
