X300 3.2 auto box advice on setting up the kick down cable

Hi all can I ask for some advance please. I have a 1997 3.2 X300 auto. The old girl is lovely to drive.
What I would like to know is how should the gearbox behave. She goes through the gears just find shifting up and down but if I am at a constant speed and put my foot down she acts as if I’m in to higher gear and she accelerates slowly. If I slam the accelerator pedal all the way to the floor she will drop down a gear but will only rev up to 5500rpm before up shifting. Is this normal?
I am still new to this car. There is also a lot of slack in the gearbox shift cable. The one that joins the accelerator pedal cable on the pulley. Should this cable be fully pulled out when the throttle has hit the max rpm stop ?