If you gain anything (questionable) by fitting an induction kit you'll lose it again if it's not taking 100% of its' air feed from in front of the rad.
Induction air temperature makes a significant difference to the power output of an engine. A panel filter doesn't cause a problem, of course, because the original cold air pipe is still used but a cone filter in the engine bay will be sucking hot air from under the bonnet, even if you try to duct air towards it. Underbonnet air can get very hot when the vehicle is running at low speeds.
Anyway, I've ebayed myself an AP22 performance meter for very reasonable money so if anyone wants to do a before and after test, and has a suitable private test track
it can be arranged, and might be an interesting exercise.
Kevin