After reading many post on flowmaster i got one put on my truck , but i went with single in single out on a 2.5 inch pipe with a 3.5 inch tip. The flowmaster is a 40 series very little drone in the cab not bad at all nice rumble you can hear it echo off buildings on this site u can also hear the gibson i had on .... Thank You.. http://www.youtube.com/watch?v=ZlKVKe5JLbY