We tested two different cold air types, and 3 different short ram types, plus 2 different versions of a modified factory box, with the stock filter, a flat panel K&N and no filter.
We tested them for peak power with the hood up and we tested them for power loss with the hood shut and the engine hot. We also ran them at the drag strip.
When we were done we took what we learned and designed our production version that we have for sale.
The short rams all made the most power with the hood up, as expected. They also lost the most compared to their own peak with the hood closed and the engine heat soaked. But the best short ram's peak was so much higher that it still made as much power as best "cold air" intake did when heat soaked.
In other words, the gains were like this:
[these numbers are approximate, from memory. We actually did these tests 2 years ago and I am not looking at the dyno sheets right now]
Short ram: Cold +8, Heat soaked +3
Long cold air Cold +5, Heat soaked +3
We also found that the air intakes that placed the MAF electronics into the tube didn't idle as well as the ones that used the factory sensor.