Got it installed and will be driving to Vancouver, BC today -- should be a good 300 mile RT to break it in. First impression is that it is very much louder inside the cabin; at certain speeds, the hum becomes a resonance that is tough to bear. I think it will mellow out after 500 miles as others have said. But, just in case, I saved that heavy, behemoth stock muffler. It does sound much more aggressive and has a "growl" at certain points. I haven't been able to open up the throttle yet to see how it performs. Also, I still have a stock air filter so that could restrict airflow until I replace it.