I wanted to get a new exhaust for my car, everything from headers to muffler. My car has a D16Y8 engine, and i intended on getting Megan Racing headers(MR-SSH-D16), and Megan Racing M-OE RS 2.5" muffler. The muffler has a 2.5" inlet and a catalytic converter i was looking at has a 2.5" inlet/outlet. I'm not sure about the size of the outlet on the headers though. My question is does everything have to have the same size inlet/outlet? Or can a muffler shop adjust the pipes to fit different sized components?