I contacted technical support at Cobra regarding the mid-range "drone" that some people have discussed and I have experienced with the 6-2-6 pipes. The technician I spoke with attributed the "drone" noise to the installation of a higher aftermarket windshield which affects air flow. My experience is that the noise is significantly reduced as acceleration through the gears reduces RPMs. He said all of their tests were done with the OEM windshield. This may point the way to some solutions for those who prefer not to have that noise. Any thoughts appreciated!