Idle speed carb vacuum issues

[Gintoff]

Hello friends. I took some time and took off and cleaned cylinder head , cleaned and tapped valves, changed pin on oil pomp's sprocket but when i assembled everything back I faced one issue: when engine runs at idle speed I cant sync carbs because vacuum meter goes wild, arrow jumps from positive pressure to negative, but when I hit throttle and in about 2500rpm, it goes almost steady in vacuum pressure. What's causing it?? :shrug: And how can I fox it, because I really want to sync my carbs and enjoy my reborn XJ Thanks for your help riders!