Equal vs. Unequal Length Headers Info The sound recording part at the bottom is interesting. Essentially it's a plot of pressure measured off the rear bumper between an OEM header and a EL Killer B header. You can see the difference in sound waves pretty clearly. EL https://www.youtube.com/watch?v=hoEoVyy4PW4 UEL https://www.youtube.com/watch?v=5sjbuqCkz24 This is a pretty extreme example being that it's a flat motor, but similar things happen on the LSX platform.