Thanks for the video!
So according to what I learned from the video:
* My O2 sensor looks fine reporting between 0.7 to 0.1 and always fluctuating
* My short term trim levels though jump up and down quite a bit though. While driving in the city usually jumps to positive +20 or so then spend a lot of time in the
negative -5 and negative -10 area. It usually is in the low side around -3 while cruising or idling.
* Long term trim levels usually either -4 or close to zero never seeing a plus.
* My air fuel ratio looks quite healthy always around 14.7 except gear shifts.
As I understand this means that it might be running a slight rich condition which does not explain the clean and shiny spark plugs with white deposits.
In the end according to the video I have to check a lot of things like exhaust, vacuum leaks, sensor health etc.
So I guess there is no direct answer here. However you might answer two easier questions.
q1. The valve clearences has never been adjusted in this car. Can it be the cause?
q2. Although I thought spark plugs were ok I am not a mechanic so maybe they are not so ok. Can this be the cause?