read my post, I was having a similiar issue. I even came to the point either fit single turbo or sell the car.
4 resonators made it so damn good especially in row rpms. even at cold start, valves fully open car does not sound obnoxious. Suprisingly car now sounds the best especially in lower rpm range lol
https://f80.bimmerpost.com/forums/sh...2&postcount=15