I've recently having a strange noise that pairs with acceleration coming from the back on my car. You can hear it more by leaning against the driver backseat. I've did some research and found out that it might be one of the components in the exhaust system has gone bad. (Catalytic converter, muffler, or worse case, the pipe has a leak) But, since I'm on the topic, I want to upgrade the muffler. I know I'll need the inlet/outlet diameters for the muffler, if anyone can help me out with the dimensions. And in general, from the ones that has done a exhaust job on their car, what are some things I should look for. I heard a muffler can hinge a car's performance, both good and bad.