Hello there!
I have cleaned up things a little in the engine bay, and hey I've found a completely broken ground link! Replaced the cable to a new one, as well as the one at battery negative. I have replaced the valve cover breather hose as it was old and hard and leaked oil. The thin vacuum hose there is quite loosy, so I may need a new one there too.

Does anyone know that to where this plugged (vac?) hole supposed to be connected? (red circle on the image)

Thanks!

moire76