Top Ten Race Muffler 409SS - 4.00 Center In / 4.00 Center Out - Aggressive Sound; The Delta Force 40 series race mufflers utilize Flowmaster s Delta Flow technology and feature excellent power characteristics with good sound reduction qualities. Recommended for all racing applications where mufflers are required with a substantial decibel reduction over open headers. Please call the Flowmaster tech-line for assistance with specific decibel requirements and applications.;