Emission Problems/Metal Core Catalytic Converter

[Yulaw]

Does anyone have any experience with a metal core cat? It's supposed to be better than a standard ceramic core catalytic converter.

The reason I'm asking is because my new catco high flow cat has gone to s*** after a month or 2 because my SR runs a little rich. I believe the cermaic element ended up like the stock cat I had before (hollow inside). I have a recirculated BOV and set fuel psi to 36 psi w/ a nismo fpr. I need to pass emissions because I really DON'T want to get an inspection sticker under the table unless there's absolutely no chance of passing emissions.

Here are my emissions readings w/ Catco cat when it was new:

The first set of numbers is the Standard and the second set is the Result.

High Speed (25 mph) HC (PPM) 132 119 PASSCO (%) 0.73 0.72 PASSNOx (ppm) 945 140 PASS

Low Speed (15mph) HC (PPM) 136 161 FAILCO (%) 0.76 5.81 FAILNOx (ppm) 1045 72 PASS

I almost passed, but that was before I installed the nismo fpr and oil changed. 2 months later, I retested after installing the fpr + oil change and the results were bad. Everything went up, and I failed all but NOx. I know my catalytic converter is the problem. The guy who inspected the car told me normal cats usually go bad if the car runs rich or backfires and I should get a "Heavy Duty" cat. So, I'm thinking of using my old stock exhaust with a metal core cat to help me pass. I only want to know if it's worth it. I don't want the cat to end up like my stock one.