i installed my snorkel just for the dust and sand of texas. after some trips i would have to vacume a half a cup of sand out of the air filter after the snorkle none has gotten in.
i noticed the temp change myself, i run a data logger on my odbII connection.
the cool air is a few extra horses (not enough to feel) but if cooler air didn't help intercoolers wouldn't be needed.
the throttle body heaters can't help on d2's, i was surprized i got the intake temp drop with the snorkel.