The Motordyne ShockWave))) E370. 
 
The best sounding exhaust made of a high quality True Dual X pipe exhaust system optimized for the highest level of torque and power by using progressively expanding dual 2.5″ primary tubes to dual 3.0″ exhaust tubing for the best overall power curve.  The sound is modest at normal cruise speed and it blasts a Shockwave))) at WOT and high RPM.