I have never really had decent heat in my 2000 XJ in the three years I've owned it.
Finally went through the process of using diluted and straight strength CLR short soaks and back flushing a good 6-8 times and removed all kinds of gunk from what was SUPPOSED to be a flushed heater core!
Now, I have plenty of heat - the type of which I have not experienced since owning the XJ.
However, what is quite noticeable is the drastic reduction in air VOLUME when switching from A/C to heat, and then as the temp is raised.
When finally reaching full hot heat setting, the volume of moving air is somewhat disturbing.
Is this an air blockage issue, or par for this year XJ?
We have removed the accuator and it works fine.
We can open and close the blend door by hand/fingers with no apparent restriction inside the plenum.
I have heat for the first time, and for that I am grateful.
But I would not want to be a passenger in the back seat in January here in northern Minnesota.
Is this a common dilemma?

Is it OK to bump?

Vary little heat gets to my back seat too, what I would do is pull the fan/motor and clean it off and out with compressed air, then clean the hole in the fire wall out of leafs an what not. That should help