The only reason I got one is because I hear that the ball and spring method eliminates wastegate creep. It might only make a 1/2 second difference in how quickly the boost builds, but it was cheap
I would think that maybe it will help with part throttle boost, at least during times where max boost is going to be achieved eventually.
I think sixto knows the results first hand..(please tell us!)

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k