Iv noticed that my SLK seems to acting slugish, like the engine is working harder when driving. Engine noise has increased slightly but no warning lights have come up. The car was serviced and MOT'ed 2 weeks ago with no problems, this has just occured today. THis did happen before, but i had to leave the country to work for 5 months, when i returned the problem had ceased until now. THink of it as driving with the brakes on but they are not. Has anyone suffered the same problem and know what it is? Or any suggestions?