Increased friction from additional air molecules is translated into pressure and temperature. The increased air flow occurs before the turbo in order for the turbo to have more air to compress to create greater mass denisity. If you have a 15lb boost,it's 2x normal not 10. You need much more than that before the mass density of air developes noticeable viscosity parameters.
These days most port injection is also sequential so the injector fires only while the intake valve is open. The size of the injector orifices combined with the pressure applied to the fuel provides all of the atomization desired.
I tried to offer the most basic of explainations applicable to both turbo and NAs. Didn't get into different cam profiles, pressure revision waves due to valve action, or changes in flow rate, denisity, pressure, and temperature caused by the intercooler.
The magic of basic physics.
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