Fluttering noise after P1SC install

[micool]

I recently installed a P1SC Procharger on a 03 GT. The car runs OK but at about 2000 rpms there's a loud fluttering noise coming from underneath the hood. ATI says this is normal and not to worry but it's loud enough to make me get out of the throttle. A few shops have told me to check the bypass or a loose connection. I've never owned a blower car before so I don't know what to expect other than the typical whine. Any help would be greatly appreciated.