Kobelco 160-vi electrical/ possibly hydraulic

Hello, I've got a few topics, 2 machines that are fighting me.

I have a kobelco 160-vi [according to cab decals, but I can't find a serial plate to confirm]. I thought it was a dash 4 but Roman numerals are hard for some reason.

I've got variable slow machine function, sometimes semi quick, usually slow. Also an arm cylinder that will boom out on its occasionally at various speeds/ positions. Im suspecting the two are at least half related because the rod seal is leaking fluid and...

Kobelco 160-vi electrical/ possibly hydraulic