So I bought the Bosal exhaust piping/muffler to replace my stock leaky one. I want to replace the piping to 2.25" so my question is can I still use the muffler and just add the bigger piping to it? Or do I need a muffler with a 2.25 outlet and everything that goes with a muffler of that size.

 

You could but it would create a choke point in the exhaust system and defeat the purpose of putting a larger exhaust pipe on