ya they can dribble diesel and it can get in you oil. if they dont pop right your fuel mileage will suffer. if there not firing right then they will run rougher.
I dont know what it costs to pop test them but im sure that its not much.
that's usually pushing it. i pop tested mine on with the equipment at the college and they tested low and dribbled. i wouldn't recommend idling for extended periods of time til you get different injectors in. if you sent them to me i'd pop test them and send them back to you for free