I have had both loved them both. I would say the AAM makes a little less drone and as for the sound with HFC I can get back to you once I install mine. One thing I like about the AAM is that its a little less flashy and is really quiet until you hit 3500 rpm or so, then is screams. I am adding z1 hfc's to see if I can make it a little louder and add a little grunt. Also for quality hands down goes to AAM.
Good luck!
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AAM Axleback + AAM Midpipe | K&N Drop in filters | Eibach Front Sway bar |Whiteline diff bushing| Dunlop ZII
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