For my application which is definitely NOT used on public roads and will never be used. N54 BMW, downpipes VSRF, subcats removed. Without those resonators it sounded absolutely awful from around 1500-2250 rpm. How the Honda Civic farts terribly. That part of the RPM range was so loud that I could hear that ugly noise while driving around the neighborhood. There was also some vibration around the B-pillars. BOTH those problems went away, he became fully civilized again. Still special sound and free breathing from the see-through design, but I'm totally blown away.