2006+ Civic 4dr guys now have a new exhaust system will help gain HP and Torque while still maintaining a quiter OEM sounding exhaust that doesn't scream LOOK AT ME from a mile a way. You will still get an improved exhaust note but not as obnoxious as some systems out there can be. For more info click the link below.
2006+ Civic 4dr Megan Racing Catback Exhaust
Thanks Guys!