Hey guys newbie here. Needs some help. I have a 1989 f350 460 efi motor. Exhaust bolts where all broken and couldn’t repair Or get a few out. Pulled heads and had a friend that’s a engine builder “say” use these old carb heads , 1973 he said and go. Had to use old valve covers and exhaust manifolds. EFI intake bolted on. It runs but have a serious amount of vacuum from her. Like trying to invert her self. Played with vacuum lines ect. But something is wrong. Any ideas ?