Yes, it will hit boost cut unless tuned properly. You can tune by seat of the pants (i.e. boost, hit boost cut, adjust, boost, etc, until you have it adjusted) or tune it on a multimeter. Multimeter is more exact.
Yes the adjustment screw is inside.
Green BCC wire is the output. White BCC wire is the input. If the unit is still in the car you will need to disconnect those 2 wires. Attach the white wire to a 12v source. Green wire to the positive lead from your digital voltmeter. Negative lead from your meter to ground. The units are usually set too low. Mine was set to 3.89v
Readings should be nearly but not more than 4.3v for 93-95 cars and 4.1v for 96-98 cars.