Adjustment screws are on the rear of throttle bodies, and are better accessible with airbox removed. Your readings are fine as they are dependent on idle speed... Just check vacuum synch at indicated 1,300 rpm idle. You want to leave the closed adjustment screw closed, and adjust the screw that is already open on the other throttle body to have both vacuum readings equal. If it's your left TB screw that is open, you will close it slightly to raise its reading to have them both at the same level.... I just set mine with airbox removed, and rear of fuel tank propped up. I covered my TB openings with the air filter foam element.