The faults are for cat converter efficiency, and I would doubt the aftermarket high flow cat would be as efficient. Which could likely result in the same fault.

Did you do any work recently that would have any affect on the exhaust gasses? (ie: secondary air system, vacuum leak repair etc.) Because when I fix certain problems it causes the cat efficiency faults (due to age of cats naturally) but once cleared the cat faults may not return for years.

I would clear the faults and drive it, and if the faults come back, then look for a source of OEM cats.

Some sites like this might carry them.

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