What the exhaust new??? A muffler doesn't do anything other than lower the noise produced by the combustion of the engine. If your exhaust smells bad and you have a significant amount of smoke coming out the end, you might want to check to see if your car is burning oil or coolant.
It's been a while, so I can't quite remember, but it might be smoking and smelling from the burning of the oil that is used to preserve the muffler in storage. If this is so, it should go away soon enough.
I was with one of my friends right after he got a new exhaust put on his car and it smelled kinda funky too. I don't remember any extra smoke though or anything like that. I can't wait to put my new Greddy on soon.