Originally Posted by Cincinnati Slim
I have some of the Boom/resonance issues in my coupe but it has gotten better with time. The Magnaflow was kinda "raspy" when first installed but it has mellowed with time (approx 4-5K miles). The hatch back structure of the coupe is part of the resonance problem. An extra resonator will help some but you may want to try some dyna-mat or similar acoustic treatment under the cargo area carpet. That open area acts as a acoustic "bass trap" and amplifies that particular frequency. This is a common problem with hatchback coupes in general. Slim
Have your wife cut out a piece of 3" foam that will fit the floor, snuggly, of the luggage area, get her to cover the foam with a nice, contrasting material that will look and wear well in that area. You place on top of the carpeted area and it will help protect the carpet as well.
You will find that it will help insulate and absorb the sound that comes from the rear.
I also put a slice of doll stuffing (it is white and almost looks like furnace filter material) under the carpet and over the storage compartment for additional absorption.
I don't have the Magna-Flow system but understand your issue.