In this stage – I do everything to the best of my ability to fix the problems of my car’s idle.
First: I replaced the ignition coils in cylinders No.2 and No.6.
After: I made and installed snubbers.

Checking the result with a final edition snubbers:

Umax reduced from 420V to 320V. Completely aperiodic transition process. Ignition switches don’t work in “clamp” mode anymore. An excellent result!
I re-adapted the engine. Drow around 200km in the city mode, very often allowing the engine to work idle.
The result:

As we see:
a. the average mechanical energy of all cylinders is exactly 0;
b. short-term difference form ideal is max +/-2 .. 3 units, which is +/-3 .. 4%.
The call-up menu shows such (typically) numbers:

Typically, unevenness in this menu does not reach more than +/- 1 .. 2 units. Rare events: until +/- 3 units in the short term.
As we see, all cylinders are working equally (un)even.
Measurement conditions:
a. outside temperature: +8oC, required power of AC compressor: 0;
b. running lights, all significant power consumers are tuned off.
This is the less favorable engine performance mode (for the rough run measurements).
A note: the mileage of the car is 230.000 km, and the injectors have not been replaced or cleaned.