00 DTS Power Steering Noise

I replaced the Power Steering Pressure hose assembly on an 00 Cadillac Deville DTS and now you can hear a hissing noise when the steering is at it's neutral postion (no load/not turning) it is audible inside the vehicle, at first I thought it was inside the vehicle but you can also hear it by the drivers front wheel and right at the rack where the lines go in but as soon as you move the steering wheel even the slightest bit it will go away. I have bled the system repeatedly with the engine OFF and ON, wheel OFF the ground and ON the ground, turning the wheel back and forth probably 500 times, and I've been driving the car for the last 2 months with this noise no matter what I do I cannot get rid of this noise. Can anyone tell me what the problem is? I did see another guy have this problem on another site and he took it back to the garage and a few times then finally just had them replace the line again and that took care of the problem (both line/hose assemblies were AC DELCO) but I find that hard to believe that it was a faulty hose.

Thanks in advance
Joe