Replaced the fluid reservoir but the noise is still present. There was some debris present on the screen of the old reservoir but it was not close to being clogged.

The noise is definitely coming from the left side of the engine and is engine-speed dependent... the higher the rpm, the louder the noise. At idle there is little change in the noise as the steering wheel is rotated either left or right.

The noise disappears when the poly-V-belt is removed... and the only belt-driven components on the left side of the engine are the A/C compressor and the PS pump. The compressor pulley sounds a bit dry when rotated by hand but with the belt installed the noise seems to come from the pump, not the compressor pulley.

External inspection of the PS system reveals no gross faults - none of the hoses are crimped, the oil cooler and rack are free of damage and there are no leaks.

The power steering system works flawlessly, other than the noise.

Any suggestions? Install yet another pump? And if its not the pump, what should be examined next?