Funny you ask, one of my very first mods was remove the black rubber pc from a Basis turntable motor and hard wire a better one. Wasn't sure it would work, and being inexperienced I used a really cheap ($75) power cord, that wasn't even worth trying to sell.
That pc on the turntable motor made about as big a difference as when it was used on amps and stuff. Since then I have done this a couple other times. Most recently was the motor on my Origin Live Sovereign.
This time I decided to use a pc that, while very expensive, had no real market value due to being a prototype. So cutting it down a bit was no big loss, and I was expecting a nice improvement.
Instead, not so much. Turns out this particular pc was too stiff. Even trimming most of the conductors, even just the few that were left were awfully stiff. I am used to thinking in vibration terms, they had to be transmitting a lot of vibration right into the motor.
So I tried eliminating this wire for the last few inches, and used the most flexible wire I had in house, cheap ordinary lamp cord, to go from the motor to a IEC connector just a few inches outside the motor pod. The IEC is then isolated on a rig attached to the back of the rack. Now any pc can be used.
Doing it this way finally got me the expected improvement. So the moral of the story, once again, everything matters. PC matters, and isolating the pc matters just as much.