The SI/DO Flowmaster 40 droned a little too much for my taste and was a bit loud for a trooper's truck, so one of the first things I did was tone it down so that now it sounds exactly like a new model Mustang GT, which we like. I did it by adding a bullet, a Cherrybomb ahead of the FM where this 28" long 2.5" OD pipe resided. Under $30 and I kept the well positioned tips and solid welded pipeset. I painted it too.