Example: If the diameter of the intake manifold inlet is 2.25in, throttle body diameter is 2.25inches too. How a spacer that I believe is bigger than that will add more air volume if the two ends of that spacer still having a bottle neck of 2.25in.
It doesn't make sense. The air flow its the same as stock there is no possible way of having more, unless that the intake manifold inlet diameter and throttle body are bored.
Right so you mean that 5-7 cubic inches more will increase all that torque and HP, come on .....
Porting & Polishing is to increase the airflow CFMs that the engine is sucking, Im sorry but this addon doesn't do that, you dont need to be an engineer or scientist to be aware of it is as simple as 2+2.
Isn't only the speed that the air is traveling, is the volume of it. If the runners of the intake manifolds where something like 1-5cm in diameter then I will take that comment as valid, but in reality they're very thick. Get a picture of an intercooler they can exchange temperatures not only for their conductivity properties, also the internal ducts are very thin. If you want I can explain it with equation I just have to find my Thermodynamics notebook.
No matter what type of dyno you use is very difficult to achieve the exact results two times, most of the runs can have differences very noticeable. Even in stock cars.
Conclusion
By reading your explanation I can conclude that adding another extension to my garden hose I will have more water?
Also another thing, be aware that using this spacer for installing a nitrous nozzle is another big error. If someone do it , the nitrous mixture will not get evenly on all the cylinders. That is the reason of the warning in the instructions that say that the nozzle must be almost one feet away from the throttle body