Any system that increases the loudness over the stock system is going to resonate more than the stock system and create more interior noise at any RPM level. The more free flowing the exhaust, the more interior and exterior noise level and there is no getting around this. If you want little resonance then you should stick to the OEM system or buy the the tequipment PSE sport muffler that has a bypass pipe that can be opened or closed via a switch. FYI, Fabspeed buys their mufflers from Dansk. This thread should clarify that issue.
http://forums.pelicanparts.com/showthread.php?s=&threadid=251829