Power steering problem

I have a 98 Deville, 4.6L Northstar, 100k miles, the power steering was making a terrible noise when turning the wheel right or left, the noise sounded like a vibrating, cavitation from the pump. The noise would stop with the wheels straight ahead. So I changed out the PS pump and the noise is gone, but the steering is not right. It feels okay when the car is moving, but I cannot turn the wheel with power assist when the motor is running and the car stationary. I did the bleed procedure that a repair manual stated, turn wheels left to right to bleed air out, still no luck. What else is there besides the pump? Can the module connected to steering linkage from the PS hoses be bad possibly, or might I have a bad pump, it's a rebuilt from Autozone?? I'm lost to this point, any advice is greatly appreciated.

Thanks

Taking a chance with an AZ rebuilt, a pressure test under the problem conditions will reveal the source of the problem, you will need the specs though to determine what is appropriate.

Yeah perhaps, I'll have to check my receipt, I think everything they sell is remanufactured unless specified. I would think it's no big deal, PS pump is pretty low tech and "dumb iron" but maybe Cadillac has some higher spec. One thing I didn't mention is odd, when I rev the engine to about 1500 rpms, the pump seems normal and I have good power on the wheel, almost normal. That leads me to think the pump I have is not putting out enough psi. At any rate, I would think the AZ pumps are manufactured to near factory spec, whether Chevy, Caddy or whatever. I'll continue to check, other feedback is greatly appreciated from anyone who's seen this problem before. Thanks!

there is a pressure regulator in the pump where the pressure line threads into the pump, check and make sure it moves freely in the pump, a small nick is all it takes to keep it from moving freely

Thanks for that advice on the pressure regulator, I certainly did not notice that when I installed it, I'll check it out.