I'm bringing the Z back to life. Boy was it in bad condition when I first received it. I've noticed there's a few pin hole leaks right before the cat where the welds are (I welded on new cats in attempt to fix the NOX issue). Before these new cats the old ones yielded a ~750ppm...the new Magnaflows are doing 1300ish. I'm suspecting the few pinhole leaks are causing too much O2 to seep into the cats and are disrupting it's ability/capacity to store the O2 that it splits up from the NOX. These Magnaflows are somewhat lighter than OEM...not sure if it's the casing or what. The Magnaflow's ability to reduce the HC and CO is great. I only drive like 5-10 mins on the freeway to the smog shop and it makes HC and CO non-existent.