I am not a mechanic, there are a lot of Members on this forum who are much more knowledgeable than me, but I would have thought that after 5 years, in case it has not been done, some basic filters check up or cleaning of filters, liquids change, spark plugs would be worth looking at.
As for what you describe - I would have thought that two topics may be worth considering: overall tune up (ignition timing, valve clearances, linkage tour, including idle adjustment) would be one. Another one would be to check functioning of the Constant Speed Solenoid. In most of the automatic cars you have the solenoid on the intake manifold that pushes linkage a bit to increase idle to prevent engine from stalling. It is activated by one of the two hydraulic switches located on the gear box. While in the car, select a gear and ask another person to see if this solenoid works.
If your car is late US version with emission control system, this solenoid, even if it is there, may not be responsible for idle increase. Then the question of general tune up comes back and proper functioning of emission control system is essential.
There is a lot of information on the forum on this topic - fairly common questions. You can spot the post through the search function.
I would encourage you to become a Member here. With the limited associated investment you would get access to virtually all you need to know about a Pagoda. All important tune up procedures are there.