Interestingly enough, the claim of +12hp is actually pretty inline with what GMC claims they get from their AT4's exhaust/intake package.
+15hp on their 6.2L V8. You can see that here on their website, and below in the screenshot.
https://www.gmc.com/gmc-life/trucks/sierra-at4-off-road-performance-package
I know I risk kicking a beehive here, but short of Ram's engineers coming here and telling me otherwise, this is my understanding (and I've read everyone's opinions on this one).
An engine is an air-pump. In the old days of muscle cars, more power meant more displacement, to pump more air.
It's why the 2.7L turbo engines Ford has, are meant to compete against Chevy's 5.3L engine - while the 5.3 Is larger, using the turbo forcing in more air, it is mimicking a larger engine.
That's also why when someone has strange power loss, mechanics will often look for the old textbook case of, "mouse/chipmunk got into the air box and left a ton of seeds, sticks, and leaves in the filter. Then died." restricting airflow. To pretend the aiflow out of the airbox has ZERO effect at all on power, is kinda weird. Which is why no one has expressly said that in those words, more just implied it using some very sly verbal sleight of hand.
I think it's inarguable that the stock airbox is pretty good, it was designed to be that way.
I think it's inarguable that with the computers, sensors, and all the other doo-dads governing the engine, it is pretty hard to figure out with exacts, what is doing what.
HOWEVER, thanks to GMC being willing to state what their intake/exhaust net gains are, plus some common sense, I have my doubts that the net effect of a better airbox is zero. I
personally think the debate is whether it's 3hp, 1hp, 15hp, 30hp net gains - and that's hard to tell.
(again, if you can lose power from a mouse setting up a hotel in your airbox, I think it's silly to suggest there's ZERO effect on the opposite).
The next debate is whether that's worth the price - and that's super understandable.
For me? I'm looking hard at the ram air.
I'd like a better flowing intake, and a mopar "Factory" unit that won't torch my warranty? I'm thinking I'm going to go all in.
I'm not expecting it to pull like a 7L V10.
And I wonder if I have to remove the grille shutters after installing this, after seeing it in the vararam thread.