If you want some more noise and power out of your Cobra then look into this Kooks High Flow GREEN Catted Xpipe. This Xpipe is to be used with Kooks Longtube Headers and can bolt up to either your factory or aftermarket catback.
Kooks Green Cats are the highest quality aftermarket highflow Catalytic Converters that you can buy, and can hold up to the power that the 03/04 cobra produces.
2 1/2" x 2 1/2" Stainless Steel X-Pipe
Includes Kooks 49 State Legal EPA Certified Ultra High Performance GREEN Catalytic Converters
OEM Outlet for Use with Stock Exhaust
Must Be Used With Kooks Headers
Greatly Increase Exhaust Flow and Power