One aspect that I've been considering is when the air is drawn up from the engine bay (below) and through the top mounted (horizontal) intercooler (e.g. with a updraft fan), it is pulling HOT air (from the hot engine bay) across the IC (and the fan motor). That will have a negative effect of the intercoolers ability to do its job, compared to pushing cool external air from above down across it. It will also shorten the life of the electric fan. No idea just how much difference it would be, just thinking of various factors involved. Although it might not apply here, on my setup the large aftermarket oil cooler is mounted under the intercooler. So if the air is pulled up from below, it will be passing the hotter oil cooler first and then through the IC. But going downward will push the cool air past the IC first and then to the hotter oil cooler. This is much like how a intercooler is mounted in front of a radiator on front engine cars, passing the cool air through the cooler IC first, then the hotter radiator.