Take it to an muffler shop then decide. It seems to me cats are cats. They're pretty straight forward devices. I got quotes for aftermarket OEM equivalents for my 90 300te from $300-600, $1800 from the dealer. Mine wouldn't pass the smog test.

My MBZ mechanic is in the same building as a muffler shop with a Test Only smog shop in between. He sent my car to the muffler shop and installed one cat instead of the three OEM's, then moved it to the Smog Test station, then back to his shop for me to pick up. Total cost...

$70 for the cat, $100 for the labor to install, $45 for the smog test and certificate, but then $2000 at my mechanic (motor mounts, rear accumulators, smog pump, blower and regulator). Great deal on everything, but it still stung.

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03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio