i must be odd man out my JLT fits great with the boss intake. it takes a little fiddling and you may have to tilt down the air cleaner a bit to clear the hood apart from that it fits great.
edit: never needed any new coupler.
i have that same sound and i notice it comes on with the ti-vct cams going into performance mode. with each tuner they can change that and the rpm where it makes that brief rattle rattle exhaust note changes with each tuner. also i think some tuners transition it faster than others - right now...
the hoods are vented for reduced front end lift at high speeds and reduced drag. this was first noticed on the 2011 302S hoods. they all were immediately retrofitted (if the class allowed it) to have venting in the hoods to let the air out the top instead of shoving it out the bottom lifting...