My Rotrex Supercharged 4-cylinder throws high CFM and exhaust decibels with 3-inch straight pipe. In an effort to reduce noise, the Flowmaster dBX resulted in significant noise reduction, but unfortunately also unrivaled amounts of horsepower and torque. The Flowmaster Pro series was installed. The noticeable increase in flow, power and torque far outweighs the marginal dBX increase in decibels. I will agree with other reviews that the black power coating scratches easily. However, this is aβ¦