The vacuum line should be hooked up while you're driving. To adjust the fuel pressure, pull the vacuum line off whil the car is idling. Loosen the lock nut on the threaded, allen head bolt and turh the allen head to adjust the pressure. You should set your combo at stock opressure which is 39 psi with the vacuum off. Hold the allen head steady after you get there and tighten the lock nut. Hook up the vacuum line and you should be ready to go.