Airflow is secondary to carb throat vacuum. The carb venturis don't exert much in the way of throat vacuum until there is a pretty good velocity going through them.
The dominant vacuum in the carb throats originates in the piston cylinder when the piston falls and the intake valve is open. Nature abhors a vacuum and that negative pressure tries to get equalized with air from the atmosphere via the intake ducting. Stock the carbs are about 1/2 way between air source and piston cylinder. For simplicity sake lets say the pressure or vacuum is also halfway between piston cylinder and outside pressure.
The pressure is important to carbs because the throat pressure to outside air pressure differential is what pulls/pushes fuel through the fuel jets. Pressure is applied to the fuel in the carb bowl. And negative pressure or vacuum is what pulls it from there though the various fuel jet orifices in the carb. Fuel volume is then determined by the pressure applied and the orifice size. It's still a pressure equalization effect even when applied to liquids.
Velocity stacks and pods both shorten the air duct between piston fall source and air inlet. This places the carbs closer to the equalization source (outside atmospheric) and effectively reduce the throat vacuum in the carbs. So, the carbs now draw less fuel through original sized jet orifices. Since there was no displacement or valve timing change, the carbs no deliver less fuel than with the original duct and air filter box for the same volume of air. The engine runs lean. Too lean and the engine can't make power under load conditions.
Venturi effect adds to the basic pressure drop as air velocity increases. However, if the basic pressure drop originates too low, it cannot compensate for the loss on it's own.
To restore the correct air fuel balance, there is no choice but to increase the fuel orifice delivery size when shortening/altering the intake duct tract. This is far easier than moving the carb closer to the falling piston vacuum source.
Very unlikely your stock engine will make more power with pods or stacks. At least not until you approach and/or exceed redline where the stock filter box begins to add oxygen restrictive factors. 1-3% is important on the track. It will be louder without the stock air box, and this tends to enhance the butt dyno effects rather than actual measured improvement.
Now you know...
Cheers,
