Why. Why would you ever buy this? You just spent $50k on a car, engineered for optimal power and fuel economy, and then you stick this on your brand new vehicle that makes a cool "whoosh" sound, and they offer no dyno results? Never mind any increase in performance, but you say the turbo sounds stressed? In a world full of bad product that is sold on no merit and purely marketing, I'd never put anything like this on my vehicle.
The whistle it goes woot woot, etc.
'13 335i EB MT