[undy]

that would be a good question.. Maybe Eric w/ Classic Chambered could weigh in on this flutter stuff???

BTW... my CC inserts without the packing and the louvers facing for minimal noise reduction were unbearably loud, hence the new Cobra Packs installed for maximum noise reduction. I'm very pleased with the sound and performance now.. I'm getting used to the flutter. I talked to a friend standing away from the car while it was running/fluttering and he said he couldn't hear it from his standpoint. Maybe it's only noticable to the driver??