Good results, nice and smooth in the delivery which is always nice to have.
As you can't squeeze any more out of it, (I know I'm stating the bleeding obvious ) you've reached the max flow of something, most likely the turbo as you said. You're seeing about 325hp worth of air flow to get those numbers at the wheels...Could also be cams or something else in the system, but I'd expect to see a different power reading if it were something else.
Anyway, great result and I'm sure the car is PLENTY fast enough!!
Congrats