With the engine warm and idling in Drive, the brake on, and wheels chocked, adjust the minimum air rate (throttle stop) screw on the rear throttle body to obtain a reading of 6 inches of water. Then recap the port and connect the gauge to the front throttle body venturi vacuum source. Using the balance screw, adjust for 6 inches of water on this throttle body. If the reading is too high, the throttle plates need to be closed; too low, and they need to be opened. Once this is achieved, using the minimum air rate screw on the rear throttle body, adjust the engine speed for 500-550 in Drive. The factory specification is 475 rpm, but Bill has found that as the vehicle ages, it likes a little more throttle opening. Since the balance is completely out due to the screw being replaced, you may need to go back and redo the manometer procedure on both throttle bodies to bring them into specification.