On my Jeep CRD, I removed the CAT and choke point in front of it and replaced both with a larger section of straight aluminized pipe and replaced the stock muffler with a Flowmaster. Jeep has a nice mellow tone and gets a little louder when you get on it hard. Noise is not bothersome at all in the vehicle and can hardly be heard with the windows rolled up and music playing!!!!
I am a firm believer that the open free flowing exhaust system helps in engine performance by lower EGT leaving the cylinders, faster turbo spool up time, and better fuel economy... I was able to confirm the EGT lowering due to adding a 5 inch turbo back exhaust system on my Dodge Cummins when I modified it several years ago since it has full gauges.... The quicker turbo spool up time and better fuel milage also improved...
