The Nuclear Propulsion Package (NPP) option is a vacuum controlled valve on the factory exhaust which is controlled by the ECU. It will open and close based on RPM and throttle position.
The valves will be open for the first two seconds that the car is started. It requires time for the vacuum pressure to build to close the valves. After that The operation of the NPP is normally closed, open on demand. Have someone stand behind the car and bring up the RPM to 3,500 and you should see the valves open. The butterfly operation is tied to the throttle position sensor and the RPM. It uses the throttle position to determine driver intent. Under normal operation the valves work as follows:
Below 30% throttle and 3,500 rpm the valves are closed. Above 30% throttle and 3,500 rpm the valves will open. Between 30% throttle and 80% throttle and above 3,500 rpm the valves are open. Above 80% throttle and above 2,800 rpm the valves are open.
Dual Mode Exhaust is a feature that allows your Camaro to stay within 'driveby noise' compliance. At 3500 RPM the valves auto bypass the factory mufflers to form a temporary straight back system which allows increased airflow at higher speeds.
3.0" Cat-Back; Dual Rear Exit with Twin 4.0" Polished Pro-Series Tips Xtreme+ Sound Level (3.0" Double X-Pipe, 2.75" Axle-Back) *Does not contain AFM Valves **Intended For Race Use Only. Not Legal for Sale or Installation on Licensed Vehicles in the State of California