Eng. Run with pax on board.
I believe that nobody in their right mind would even contemplate PA or MPA runs with pax on board.
As previous comments Airport and Maintenance SOP,s would dictate if allowed, that a ground idle run could be carried out. No problem to do so, I have as maintenance a few times.
I totally agree with the prior statement to de plane a B747-400 causes to say the least, major difficulties for Airport and Airline staff, imagine a high density A380.