Originally Posted by MoulaZ

How come the sound disappears just by shutting it off and turning it back on? That doesn't seem right at all to me. I get the feeling I may have under greased it. The only remote idea that makes some sense when I think about it, is the grease while liquefied is spun outwards and not lubing properly while the turbo is spinning, and shutting it off allows that liquefied grease to pool a bit enough for it to lube the shaft (or get to somewhere it's needed) so that when starting back up again the sound is significantly mitigated.

And yes, I can hear it spin down when shutting the car off when hot (takes about 40 seconds last time I counted), and I don't really know how to describe it and the phone mic may not be picking it up but it sounds different to the noise it makes spinning down.

Also in that clip you can hear another odd noise between 0:10-0:13 & 0:17-0:23, like this odd whining down that repeats every half second or so.