I just put on a Flowmaster Super 40 Series Muffler. It sounds stock, how do I fix that?

 

is it a 3" input out put 2 1/2 or what? .... if its a 2 1/2 try taking off your tailpipe and just putting a turn down on it, you will get a little bit more gain that way also... thats the only suggestion i have.......