Codes p0420and P0430, Catalytic Converter?

In June my car developed a leak at the clamp where the Y pipe meets the engine. I took it to a mechanic who replaced the whole pipe. I began having issues with misfires, and the o2 sensor they installed was faulty, so I took it somewhere else. They replaced the newly replaced o2 sensor and all was good.

In September I began intermittently receiving codes p0420and p0430 for both catalytic converters. No other issues. The car was running smoothly and perfectly. I took it back and had the car checked thoroughly. Had catalytic converters replaced under warranty.

Immediately after replacement, the car started whistling and losing power. No code but it had been inspected by 2 independent mechanic shops who said there was nothing else wrong and that it was a catalytic converter. Has it replaced again and immediately off the lot was whistling and sluggish. This is the third replacement in under 30 days. Each time it goes bad within hours and has significant blueing.

There’s no code and when the converters are removed, it runs perfectly. All of the tests show nothing wrong. I took it to both a general mechanic and one who specializes in engines. Both say the issue is in the catalytic converter. We had the fuel injectors checked Live test. We had the engine checked over thoroughly. We haven’t gotten any misfires or fuel trim codes.

Today we took it back for another warranty replacement. The shop said they got a faulty MAF code. However, I dropped it off with no codes, no lights. There haven’t been codes or lights the entire time.

Is it possible the MAF is the issue? Or is the code (p0101) a symptom of the clogged converter? Or is the MAF failure what’s causing the converters to go bad? The dealership won’t even touch it because of the aftermarket catalytic converter install, and I am out of ideas and out of money.