Had the S4 up on lifts today and noticed something odd. With engine idling, my ear next to the each intermediate muffler, the passenger side resonator sound is "bloop bloop bloop" but the driver side resonator doesn't make the sound. Is it possible the right resonator internals are coming loose? I think an RMB is in my future, but wondering what my options are for replacing the intermediate mufflers with something else?

 

Perhaps a misfire on the passenger side?

 

Engine in good operating condition with stock exhaust system, passing emissions test. Starts easily, idles and revs smoothly, good throttle response, pulls strongly, burns no oil, good gas mileage. Wouldn't the two cylinder bank exhausts see equal back pressure, even if one cat or resonator is clogged, since there is a crossover ahead of the cats?