I think the "seat of the pants" dyno is misled by the fact that the spoolup with a bigger intercooler is much better. So you feel like it's kicking you into your seat harder.
By proper ducting I mean external ducting to the intercooler. Proper placement in the car's airstream, or proper management of the airstream to duct air over the intercooler. The actual piping to and from the intercooler contributes little if any restriction. Stock Saabs make their power off boost, not flow.
A number of people have dyno'd T7 engines with a better intercooler only to find they lose horsepower because the engine adapts downward for some reason. Same thing with an upgraded exhaust.
I think if anything these results show that the stock intercooler is adequate at flowing (though not at cooling) and that no more than roughly 1 psig of pressure drop will occur at full boost.
Could be better I suppose. But a larger intercooler won't make as much improvement as a better placed one would. At least IMHO.