2003 Nissan 350Z POWER STEERING ISSUE

I BOUGHT THIS 350Z TRACK LAST WEEK, IT SEEMS STEERING IS REALLY HARD WHEN THE RPM IS LOW BUT WHILE DRIVING LIGHT AS A FEATHER. (WHILE MAKING A SLOW TURN IT ALSO GETS STIFF). NO NOISE OF ANY KIND COMING UNDER THE HOOD. I SPOKE TO THE OLD OWNER HE TOLD ME THAT IS PERFECTLY NORMAL. I DONT THINK SO, WHY, IT IS IMPOSSIBLE TO HANDLE WHEN PARALLEL PARKING.
WHAT COULD BE WRONG? PS PUMP OR RACK & PINION? I HAVE CHECKED THE FLUID AND BELT, EVERTHING SEEMS FINE EVEN THE FLUID IS CLEAN AND NO METALLIC PARTICULES INSIDE THE RESEVIOUR. WHAT IS THIS THEN?