Check the cabin air filter. It is located under the dash on the passenger side of the cabin. There are two screws and a couple of clips to move to access it. When I changed the one in my 1998 SLK 230, I recovered acorns and tree leaves. Blows much better now.
Mercedes-Benz SLK-Class was created in 1997.
There is a discussion board for the Mercedes SLK at http://www.slkworld.com/.
The 2011 Mercedes-Benz SLK-Class has a V6 engine.
The 2001 Mercedes-Benz SLK-Class has 16 valves.
The 2007 Mercedes-Benz SLK-Class has a V6 engine.
The 2009 Mercedes-Benz SLK-Class has 24 valves.
The 2009 Mercedes-Benz SLK-Class has a V6 engine.
The 2010 Mercedes-Benz SLK-Class has 24 valves.
The 2006 Mercedes-Benz SLK-Class has 24 valves.
The 2008 Mercedes-Benz SLK-Class has 24 valves.
The 2002 Mercedes-Benz SLK-Class has 16 valves.
The 2005 Mercedes-Benz SLK-Class has a V6 engine.