The standard air intake flows more air than the engine can use, even with a pulley kit. An aftermarket intake is a waste of money unless it is for appearance only. There are no aftermarket kit available for the car anyway. You would have to modify one for another car.
A member of benzsport.com and mbworld.org spent hundreds on a custom carbon fiber intake and on modifying a Pipercross intake. His best effort yielded 2 hp on the dyno. This is within the standard error if the dyno. In other words, what gain, if any, was not really measurable. His other attempts reduced hp.
Save your money and get a pulley kit, or a chip or both.
The way the factory routes the filter between the motor and radiator is great for intake temps below 60 degrees farenheit but for summer temps, its too hot for stop and go driving which I do a lot of from rush hour traffic. I am looking into using the SLK intake plenum and route the filter or filter box at the empty space below the passenger side headlights. Will post pics and results this weekend.
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