Review on Flowmaster 14020100 Pro Muffler Aggressive by Ron Thomas

If you are looking for an aggressive sounding muffler that will match or exceed the fuel efficiency of a straight pipe on your diesel truck then this muffler is not for you. The commercials tell you all that, but it's not true. I've ridden this muffler for over 1000 miles, measured MPG after each fill up and have been disappointed every time. My mileage is down 1mpg after my straight pipe was removed and this muffler was professionally installed. Not only that, but the time it takes to spin up my turbine has increased noticeably. This slows down the acceleration. As for the aggressive sound. don't expect that either. This muffler sounds no better/worse than the factory muffler. Revain may have a better price, but Flow Master doesn't have the best muffler for a 3/4 ton diesel truck.