Always love Akra systems.
Had one on my E92 ESS VT2 600 set up and no drone. I removed the inside of the cats http://www.m3post.com/forums/showthread.php?t=424713
Even after the removal it still sounded crisp and no drone
Now I have an evo system installed in my E90 with VT2 625.Vibration at low RPM in the cabin is terrible. Everything buzzes and rattles and you can hear me coming from miles away. I have no idea why this one sounds louder. Its cool after 3000 RPM but under its crap