I like the Flowmaster 40 series Delta Flow, or the Flowmaster 50 series Delta Flow mufflers because they aren't quite as annoyingly loud as the Original 40 series. The Flowmaster 40 series and the Flowmaster 50 series mufflers both use the Delta Flow technology, This technology enables the mufflers to produce a powerful aggressive sound outside of the truck, yet at the same time, they lower the amount of sound in the interior of the truck. This makes these mufflers a great choice for drivers that drive on the freeway every day. Believe me, at highway speeds, The Flowmaster Original 40 series muffler can get awfully annoying and cause headaches. I used to have an Original 40 series on my truck, now I've switched to the 40 series Delta Flow muffler, and I love it. Its loud on the outside and sounds deep and aggressive, yet there is little interior noise. Of course the Flowmaster 40 series Delta Flow produces a more aggressive sound than the Flowmaster 50 series does, But thats because the 40 series Delta Flow has only 2 chambers just like the Original 40 series. The 50 series Delta Flow has 3 chambers, which produces a little bit of a milder sound than the 40 series Delta Flow, but it still sounds really good. Check out all the different Flowmaster mufflers, they all have a purpose, you just have to find one that fits your needs. Magnaflow Cat-Back Exhaust systems sound really good, there aren't as loud as the Flowmasters, but they still produce a good sound. They kind of produce a sound that is aggressive, and mild at the same time. Good Luck with your choices.