Hello, I just got my 500SEL back from the shop. Apparently the catalytic converter was at fault and since most of the exhaust system was pieceed together from universal parts, they replaced the whole thing.
Anyway my question is: does running without a cat make a big difference? The car is incredibly slower now than before and I'm wondering if it's solely because of it having a cat now.

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1985 500SEL 124k miles
2001 Honda Civic EX