I had the Dr. Gas and it droned like CRAZY with my Flows.
It was a bit raspy too.
Sounded like water flowing through my exhaust.
Idle sounded great though and at WOT it screamed and howled!
So, I had some hi-flow cats welded in.
This helped, but my head was still buzzing from the drone.
Put my Stock H back on.
No more migranes.
I'm looking into the Pro-chamber now.