The problem is that what all the profiles you've tried have in common is that none of them were made on your machine in your environment on your media.
They may or may not even be good profiles, but they don't describe exactly how your machine prints, again, on your media on your machine and in your environment.
And what's worth repeating is that your RIP has no idea how your printer prints. All it does is convert pixels into dots based on the information in whatever profile you tell it to use. If that information matches what your printer prints, matching colors -- including grey -- is easy.
If not, it's not.
And the reason you're having trouble with grey is that if you're using a profile that is off by, say, 5% to how your printer actually prints in the conditions in which you're using it, in 'pleasing color' situations you're likely to not be too offended by that difference either in saturated colors or even in unsaturated colors that lean to one shade. But since a neutral has to be neutral, and since odds are most of the profiles you're using don't even start black till around 30%, that means that most of your grey builds are going to be predominantly CMY, or more accurately, lclmY.
Be off then by even a tiny bit, and you will not get neutral.