Okay initially I had a terrible internal buzz with this thing on my 2002 BMW 330ci. I was so close to taking it off after 2 days and going back to stock it wasn't even funny. I don't know how, but after a few hundred kilometers the hum has decreased significantly and now it sounds really good. It's true that when you let off the gas, there's definitely a bit of judder, and that's great. I left both resonators on and am happy with this volume. The finish also looks very nice, definitely impressive for the money.