Where Does the Extra 5 hp Come From?
 

Just wondering if it’s the red paint on the intake?👀😉

i guess increased diameter and real EL tube of header tubes, a bit better intake system and filter, optimized tune and better intake manifold

Well that’s not fair. 👀

why do you care... my17 tune is also annoying, with the closed loop wot thing.. just change header on your car and get a tune and you do better than a my17

It just seems odd, plus if anything I’d add it to the auto as they make up a higher % of sales, and they could probably use it.

Because MT master race duh! ;)

Trickle Charger: tuner doesn't have to take into account that same tune should work on tens of thousands of cars with some manufacturing variances and across the globe with VERY high variances of available fuel quality and very different climates/heights above sea level. Manufacturer engineers are capable of a lot of things .. but i never heard of high volume production car having as pre-sale prep procedure also individual ecu tuning.
Also unlike tuners that wouldn't care about that and often for sake performance even willingly compromise (eg. cat deletes), OEMs have to be very considerate about emissions & certification of car to pass standards. See for example ATs (or MTs too in some DMs) lacking these new intake/exhaust bits, as otherwise car won't be able to pass latest emission standards.
It's not that OEM cannot get more performance or don't know how .. due specific reasons they choose to not bring more then those +5hp in MY2017. If AT couldn't pass emission tests with new bits of intake/exhaust/FD .. nothing to be done with that just bite the bullet. Actually given strictness of latest EURO 5/6 standards FA20 already is pushing remarkably a lot for 2lr NA 4-banger. I doubt even someone like honda would be able to push out revolutionary more & still keep latest emission standard compatibility. There is a reason after all for latest Type-R to go turbo.
Tuners have less restrictions and more freedom to get from these cars/engines more.