I have the magnaflow on my C and I love it. I recently took it on a road trip from LA to San Francisco & back and it sounded great the whole time. I get lots of "damn that sounds sick!" comments in the parking garage at work and it opens up real nice when you stomp on it. I like the Borla too but it is a little more subtle and european sounding and I wanted american V8 tone ... and I got it 
As far as the 4cyl "drone" there is a change in pitch (but I would not call it loud or buzzy .. just a different tone) but I only notice it with the stereo off & windows up and if I'm looking for it.. On a day to day basis normal driving I never hear it switch.
As far as the 4cyl "drone" there is a change in pitch (but I would not call it loud or buzzy .. just a different tone) but I only notice it with the stereo off & windows up and if I'm looking for it.. On a day to day basis normal driving I never hear it switch.
