Bad diesel noise-wtf is it?

Been chasing a scary noise that sounds like a power steering pump failing, except that mines rebuilt recently.
Seems to come on with heat soak, not so much cold.
RPM related, comes on over 1000 rpm, goes away under 1000 rpm.
Then sometimes it doesn't come back over 1000 rpm, and more and more often it is coming back over 1000 rpm.
Thought maybe a failing (squealing) water pump shaft/seal/bearing. Replaced it, no luck.
Can the diesel fuel pump make intermittant noise like that?
Can the balance shaft(s) do something weird?
All belts are brand new, both timing, both accessory.
Had the alternator rebuilt last year, it failed in less than 12 months, now I'm running a junkyard alt with 110K on it, seems to make electricity. Could be making the noise, have no spares unfortunately.
Tried to record the noise with my phone, I'll see if I got a wav file to post.
Any ideas?

Did you replace all the pulleys in the timing set? The tensioner and such. That's what caused isues with my 2.4L. Also the alternator has a vacuum pump on it. Theyre separate entities so don't rule it out. I don't think the injection pump would make a noise like that and it's an expensive gamble to rebuild one and find out. Try to see if it changes under heavy loads or light loads. While steering or not steering, etc. Turn on all lights and electrical loads and see if it makes a difference, etc. Find what makes it worse or more prominent.

you could have air in the power steering that is causing the noise - follow the procedure in the manual for bleeding the steering box and cycling the steering to remove the air in the system. if the pump cavitates due to an air bubble, it could fry it or cause excessive pressure to spike due to runaway when it get fluid again.

Thanks for both ideas gents. The PS bleeding sounds like a real possibility as my rebuilt box and pump are both leaking worse than before the rebuild (local house, go figure). I didn't expect to need tensioner pulleys at 80k miles, and they spun smooth, so I didn't replace. Gonna go read the manual and bleed some more.

Problem identified: the rebuilt box is blowing fluid out the adjustment screw, dropping the fluid level. Had to re-bleed half dozen times to get it as good as it's going to get. Will have to refill constantly until I change boxes.
Thanks Pennyman for ID'ing the symptom.

Most people don't know that fitting is there or what it is used for. It looks like a grease fitting, but a grease gun won't fit it. Glad I helped you find the problem