I had a similar issue when I converted my car to hydroboost as well. (another guy on here had the same issue at the same time so I lucked out on the fix).
So just as a precaution try this - there is a port on the power steering pump (top towards drivers side) where the hose connects. Remove the hose and get a skinny screwdriver or I used a skinny allen wrench. There is a small hole in the middle of this port. Stick the screwdriver or allen wrench into the hole and try to push down. There is a valve and a spring on the other side of the hole. If the valve is stuck you will not be able to push down on it or feel any movement. If thats the case, get a 7/8 socket and remove the port on the power steering pump (it threads in to the pump itself). There will be a valve (looks like a lifter maybe???) and a spring. Clean them up and lube them with fluid and reinstall.
When I did this, the whine got better but I had ran it for a little while and I think it screwed up my pump before I caught it. I mean it whined badly just at idle. I replaced it with a remanned delco pump and its been perfect since.
Just another thing to check. It worked for me, thought Id suggest it. (reminds me I really need to get my old pump out and take pictures of the process)
