Have 2 different gaskets but both not matching the lower small ports, what are these for? They feel like dead end but not sure for 100%..

 

on the USA spec S4 NA they are for the port air injection.

 

Port air injection means air pump injecting air into exhaust? So if i leave a gap it will act like micro open exhaust?

 

yes, for emissions, Mazda injects air pump air into the exhaust ports, they call it port air. the US spec S4 NA uses those end ports because the EGR is in the center. everything else uses the middle.

not sure how the Thermal Reactor system works, it uses air pump air, but i'm not sure where it goes