Jon Kaase Uses Finger to Test Airflow
Notice the flow goes both ways........LOL wonder when that happens.
Here's something else you didn't figure on, looking at the pressure pulse at the top of the runner it was weaker also that large plenum dampens the pulse because the air/fuel mixture has weight and the exhaust gasses have to get past it. Notice all that fuel on the walls of the manifold build up at WOT, well what's putting it there? Notice how it pulses?
Now go place injectors just before the intake valve or in the port and ask yourself what happens when the injector isn't cycling what is there to dampen the exhaust pulse heading back up the runner during the overlap period?
A flow bench will tell you nothing about what actually happens in a running engine.