I'm running a single Spintech Sprint-trap (sprint car muffler) and I love the way it sounds, very aggrssive. As other's said it's damn loud, I ended up putting a side pipe on mine to quiet it down in the cab (ran it dumped for quite a while). I only get a drone when crusing at about 40-45. Otherwise since I put the side pipe on it, it is quite quiet in the cab until you hit the loud pedal.