According to Shiv the ignition advance multiplier goes to its lowest setting after an ECU reset which would mean any gains right after an ECU reset would be caused due to an aftermarket part being installed.
Yes... after you account for the IAM setting giving you a 10 to 20hp gain. So... um.
The 12 hp gain may in fact come from the setting and not the intake. The ecu pulls timeing after a knock event... intakes do not cause knock. The just dont do much.