I left mine on...some like em off some don't. Here is a bit of info for ya though.
Exhaust resonators provide a wide array of benefits to vehicle owners. Aside from reducing the noise from the engine's exhaust system, resonators also enhance overall engine performance and smoother driving because more horsepower is yielded without wasting as much fuel. Noise suppression also helps in passing fuel emission tests, as the resonator prevents chassis rattling, an effect that usually leads to contaminated fuel emissions.