I'm running 40 Series Flowmasters. I did it because i had Glasspacks with Echo Tips on there before. I work at a Casino and come home at 4 in the morning. I did it out of consideration for my Neighbors. The Flowmasters are Quieter, but they're by no means in the range of "normal" Mufflers. I Put some really wide tips on the ends of my Tailpipes and it made em sound a little louder and a little more Throaty. I highly suggest that you get the 40 series Flowmasters. There is such a thing as too loud. Of Course, you could always go with no Mufflers at all, but that would be illegal.