Well, I suspected that I wasn't getting a lot of air flow from the HVAC system. So, while changing the oil and doing a few other repairs, I changed the cabin filter.
Service Manual says every 5 years or 60k miles!
This is after 2 1/2 years and 16k miles.
So, I think I will start doing this one every year, like my other vehicles. Even though this one is a pain to replace.
Air even smells better.