I think the simplest issue has been overlooked: at high speed the fan and associated ducting or whatever is going to hinder the air getting past the intercooler and you'll get less airflow, reducing its performance.

Or, if somehow you get a fan in there powerful enough to draw more air than would naturally pass through at high speed, it will need a fuck tonne of power to do so. Means larger draw on your alternator and larger load on the engine. So any minute gains would likely be countered by the alternator.