Why do CAI's tend to lose some power down low and get it back up top with short ram's being the opposite?

 

Bump for you

 

its all about the flow, in the low end, the engine isn't pulling as hard, therefore the short ram can feed more air faster, as it is a shorter pipe

then up top, the engine is pulling harder, and the long pipe forces the air to gain more velocity as it travels through the length than a short ram