Boost gauge not working

The boost gauge in my 84 svo doesnt work and i dont want to take out the gauge cluster because its so perfect and i dont want to brake anything. I already unbolted it once but didnt disconnect any thing, i just moved it alittle to the side and checked the vacuum hose and it seemed to be connected and in good shape. But i dont know what hose to check from the turbo to the vacuum tree. Can any one help me identify the hose i need to look for?

Thank you!