What ever size exhaust you go with, get the same size flex-pipe.
Mine is off a V6 Dodge (Stratus or Avenger or ??) its 2.25".
If you go to an exhasut shop and have a custom bent exhaust they'll ask if you want a resonator, just tell them no.
As for the muffler, I forget which one I have.
Just make sure its highflow.
