With the BHAF, and Rip Rook 4" exhaust, I can really hear the turbo. But, at idle I can’t really hear the turbo out the exhaust. I have heard a 3" straight pipe, and 3 1/2 Banks with a restrictive muffler that have much more whistle at idle. As soon as I step on the go pedal, or when decelerating, the sound is quite noticeable.
Mike