I have a C220 CDI 2008 and was just wondering if i was to change the muffler to try and make the car sound sporty would me getting someone to change the muffler wreck the cars performance?

 

If it's just a muffler change then it should not affect your performance much.

 

Its said that trying to get a turbo charged diesel to sound better is next to impossible. Even MB don't offer the sport exhaust that they do on the similar sized turbo petrol. I remember this from when I was choosing the options on mine (C220 CDI) when ordering it new. But good luck, if you do manage it be sure to post it here.