But more importantly the turbo compressor surge is gone too.
After needing a friend to weld out one of the hex 5mm bolts on the DV that I stupidly stripped, I replaced the DV with an OEM Rev G.
Here's the old DV, which easily got stuck at a strange angle when pressed, but didn't have any tears in the diaphragm. It was a Pierburg Rev C:
And here's the turbo flutter with the old DV:
After changing to the rev G the sound is
completely gone, all that's left in it's place is a quiet 'pssh' every time you let off the accelerator.
Apparently the sound before (which I now realise was the turbo surging) is not good for the turbo, so it's good for the performance and turbo's lifespan that the sound is now gone, but it makes me sad as it was something I really enjoyed