Someone had installed an air filter on my car that was made for a different engine model and there were air leaks in it apparently because of that. How would that affect the driving?
PS It was already replaced. I am just curious to know.

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currently just 1989 300SE 185k miles

No worries mate.
Unless you drove the car thousands of miles, on dirt roads, you have nothing to worry about ( other than the guy that installed the wrong airfilter ).

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2007 C 230 Sport.

I mean like would it affect performance or fuel economy or vacuum?

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currently just 1989 300SE 185k miles

NO !

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2007 C 230 Sport.