To answer Severum 17's question, they are separate. I guess I should've explained all the gory details of my dead cat from the beginning. My exhaust manifold was cracked,(which is another common problem with this engine) according to my CarFax, it was replaced at 90k,it now has 130k. After replacing the manifold my mechanic told me my cat ,(CarFax stated that this was also replaced at 60k)was supposedly melted,(may have been BS), no PO420 codes ever came up. So after taking advice from someone at a parts salvage yard, I went and bought a cheap amazon cat. ($120),instead of paying over $600 at a local parts store. I did do a little online research and read reviews before purchasing and came to the conclusion that they do work most of the time. The PO420 code popped up after only 5 days, tried replacing upstream and downstream 02 sensors to no avail. I posted this thread just to find out if any other members have ever had any luck with the cheap cats or any similar situation. I did remedy the problem as posted above, it may have been the fault of an inept, greedy mechanic, but It definitely was a big pain in my A$$!!!