I get better gas mileage.
I have zero done with my exhaust. (You've seen the video, you cant hear it unless you're foot is in it)
There is no noticeable loss of power or torque down low. There is a gain in mid to high RPM.
I'll be doing a dyno soon.
Finally, I don't think you'll find any MMW headers left. He had one set left and if they are gone he probably wont be making any more. Would be best to check his facebook page.