I just bought a 2005 4wd chevy Tahoe. I've been noticing a little metal on metal vibration noise, that I believe I've pinpointed as the metal surrounding the cats is degrading/rusting and vibrating intermittently and I can hear it. I would just assume keep the same stock noise level, as it is not very loud, and my wife and I like that (its her daily driver). I don't really want to spend $1000+ from the dealer for stock replacements, and was wondering what others have done? I could just delete them completely, and go have the rear o2 sensors turned off, but I was concerned how much the noise level would be elevated by doing that. Any help is appreciated.