I'm kinda surprised you have a drone with turbos (triple pass). Most complaints I've heard are from two chamber flowmasters, and their clones.
You could try something like an ultra flow straight thru, but it will be louder than your turbos.
I would consider a pair of glasspacks in the tailpipes, as resonators, to cancel the drone.
The helmholtz definitely work, but require some math, some experimentation, and some fab skills.
