Duke: I don't have a multimeter which can measure duty cycle so I measure voltage on the X11 socket and calculated the duty cycle from the voltage.

Sugar Bear: All those hoses are looks good to my eyes. The o-ring around the dipstick was replaced so should be good. There are some joints around the thermovalve which are bad so I ordered all of the small joints around the KE jetronic vacuum and will replace them once arrived.

Today I checked what happens if I unplug the O2 sensor and absolutely nothing changes. So the duty cycle slowly goes up to 92%. In this case the duty cycle should be at fixed 50%.

I will try to figure out why this is happens, but I would appreciate any idea.