1999 Pontiac Grand Am Power steering gear box or pump

I worked at a cadillac dealership and was told my the repair shop I needed to replace steering gear box, I bought a used one with 22,000 miles on it a few months later. No longer worked at dealer so I took it to a auto lab and asked them to replace it, they said they would take a look and make sure thats what it was, they never did, mechanic sat in my car and turn the steering wheeol back and forth and confirmed thats what it was. After being replaced it did the same thing took it back to same place they tell me its the steering column, replaced that. Not the problem. Anyway driving my car yesterday and it started making a hummin or buzzing noise from right side of car under hood, when turned left or right hear a real bad noise, getcousins, he check power steering fluid, almost gone he fills it. I drve home hours later still hear noise check fluid when get home needs more, sound gone. Next morning check fluid, not empty but little less. Drive car to work this morning no noise. Cousins seem to think could be power steering pump. Or could it be rack and pinion again? I hope not. Ugh Thanks in advance. By the way the owner of auto lab refunded the labor costs for the steering column since they told me it needed to be replaced when it didnt.