I noticed a very loud throaty sound from my exhaust when starting my 2001 SLK 230 the other day. The check engine light just came on also. I lifted the car to check for any problems or leaks in the exhaust but I could not find anything. I went to Advance Auto and the diagnostic stated a misfire in cylinders 2 and 4, a throttle sensor, and an uptown oxygen sensor. That's alot of things that could go wrong all at once. Any suggestions?