I'm looking for an aftermarket direct-fit catalytic converter for my '91 Mercedes 190e 2.3. I was wondering, which brand is better: DEC or Miller?

Also, it is a California car, but right now, it's registered and driven only in Arizona. It currently has a cut and weld universal cat on it. Would it be ok to use the 49 state diect-fit version in order to save money?

Any information would be appreciated.

Thanks.

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2000 c280 Sport (looks like an upgrade, feels like a downgrade)
1991 190e 2.3 (sold)