"The smoke
is pumped INTO the system, with the engine not running - under a low
pressure to force it OUT through the leak."

Yeah you could brush up bit as well. It must be tested with the engine running. When you shut it down at east ONE intake valve will be open and the odds are good that it is during valve overlap, which is quite long in modern engines. Odds are even better that two intake valves are open and it will go in one and out the other.