catalyst converter was fried and had a hole in it? on 2002 Nissan Altima

car has 118,000 miles. My cousin who is a mechanic recently replaced mass air flow meter about 5-10,000 miles ago. Now a code came up I believe it was p0420 low threshold for cat. To get to the point he replaced the cat and the old one had a hole in it. Were not sure if it is being caused because we replaced the mass air flow with a used part from the junk yard, or if it has to do with the fuel pressure. Were also thinking the bad cat may have shot debris into the last cat in back of car. Has anyone experienced this or can anyone shed some light on the situation. Please help. Ps. With Nissan I need to get an adapter in order to test fuel pressure what the F! Please help

Asked by for the 2002 Nissan Altima
Where was the hole in the CAT? Was it split or was it a clean hole and how big. I don't usually hear of Mass Air Flow Sensors putting a hole in a CAT. If they run too rich or lean, they will set a Check Engine Light. I don't think that fuel pressure would burn a hole in the CAT. You would get a Check engine Light way before that happened. Why do you think that the hole was cause by the sensor or fuel? Was it a burned hole? By the way, many cars need special adapters to check for fuel pressure. I have over $2500 invested in just fuel pressure adapters and fittings in my tool box.
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