There is a subtantial difference for the whole run with a good cold air pickup. I mean a good one that always only gets cool air, not just a path to outside air directed at the filter. The important point is to not heat soak the system to the temp of the underhood air while waiting before the run. If you pick up only cold air while idling in the lanes, the whole system will start at about ambient temp because the IC has been cooled from the inside out basically by the ambient air. If it's say ~ 70 deg out, you'll start (and end) the run some 30 deg cooler than if you start with IAT at ~ 100 deg, like many filter near the radiator setups do. On a 700 hp mill that's about 35 hp worth of air density increase during the pass, which is on the same order as choosing an fm IC vs a good stock loc IC in the first place. I'd call that pretty signiifcant. I have log files from my own car showing what I've described. On mine the 14" K&N cone filter was totally enclosed, and the duct feeding it was 5" dia. The pickup was a custom plastic molded piece at the front lower corner of the car. Molded by Frank Fertita in San Antonio, who was also going to do some of the shrouds for CAS back in the day...
Plus, FWIW, last time my friend ran his low 11's/high 10's car with a PTE fm on it, in some unsually cool night air (for us), his did show a substantial drop in IAT during the 1st half of the run or so, Then IAT leveled off and started moved up from there. He has no cold air pickup and was leaving the line around 100 deg. He does have a FAST so we have logfiles that show this too if anyone cares. FWIW. YMMV.
TurboTR