hi slater
check your hitting the sweep spot as you can lose 20 yards with hitting it out near the toe or heel, the modern driver is so forgiving you might not see or feel its in the heel or toe, try talc on the club face to show where your striking the ball. if you down about 20ish yards thet might be what it is, i set up with the ball out near the toe of my driver and it hits in the sweep spot when i set up like that.
bill