I can attest that this cat back has zero drone when cruising. And this is due to a well-designed Helmholtz resonator which is designed to cancel out certain frequencies.
It works so well that it inspired me to fabricate a quarter wave resonator for my S2000, which had terrible deafening drone between 3000-4000 RPM. The quarter wave resonator is not as effective as the one on the CP-E cat back, probably because I only used 2" pipe, but it eliminated all drone from around 3300-4000. Still some slight drone between 3000-4000.
Check this out.
Before...notice the huge spike which caused my ears to ring:
And after...
I'll be making a DIY thread soon once I finish making a video. Would be a great addition for the MBRP, Injen, etc guys who want to eliminate drone.