How can one do this and determine if its affecting the performance of the car.

 

Mine rattles at idle and sometimes during acceleration up to 3k rpms. I have 110k miles on the car. Also, when I first start up and car and drive away the car will sit at 2000 or 3000 rpms when trying to accelerate and then all of a sudden surge, but I'm not 100% sure if that's related to the Cat. I bought the RT Cat from Excelerate, just waiting on some warm weather so I can throw it on.

 

There is no rattles or anything. The only thing is that all of a sudden a few months ago the exhuast just alot louder and agressive for a stock exhuast. Didnt really pay it no mind that it would be a problem and just looked at it as somewhere between the header and the the mufflers something to dappens the sound has broken up and now more exhuast is flowing which I thought was probally a good thing until now. Its definately something from the header back hurting the top end because the motor was dyno tuned a few weeks ago and is running strong.

 

do u have headers? could be a torn flex section