Well my mechanic said it is the pump... but I am postponing it because I lately had to pay around 1K$ in cooling system repairs, so i'll wait till the next oil change to replace the pump and confirm that this is the culprit... meanwhile I am trying to adapt to the groaning and moaning :) the pump cost 200USD here, and there is one for 90USD (Taiwan)... since I might be upgrading to the E70 in a couple of years, I might go for the cheaper one...

I purchased my truck used, and it had the same groaning noise once you turned 80-85% the steering left or right.
The ATF fluid was quite brown and almost muddy, so probably never touched. Also, the PS hoses were leaking - I replaced them and changed the Oetiker clamp with a screw-on clamp. I replaced as much ATF (Mobil 1) as I could, short of performing a flush, doing the turkey baster method. I went through about 2 - 2 1/2 qts in about 2-3 days. The ATF fluid in the PS reservoir is now pink and clear for over 1 year now. The groaning also disappeared.

0.02