there is a vac line that will go to the box. when your manifold starts to pressurize so will the vac lines and it will go into the box.
and i am guessing if you turn the knob all the way to nothing then it wont retard anymore than the factory computer will. i havent used one myself so i'm no expert.
and i am guessing if you turn the knob all the way to nothing then it wont retard anymore than the factory computer will. i havent used one myself so i'm no expert.