Pretty much normal for most engines/vehicles
14.7:1 air fuel ratio is a WEIGHT Ratio
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline
The reason a 5 liter engine has more power than a 4 liter engine is because it can pull in more air so can burn more gasoline to release more power
"Hot air rises"
Why?
Because hot air is LIGHTER, weighs less than cooler air
The point of a Cold Air Intake is to pull in the coolest air possible so computer can add the most gasoline to release the most power
As air gets warmer it gets lighter so power will ALWAYS go down
Adding more gasoline just gets a flooded engine not more power
Adding cooler or more air will allow more gasoline to be added and more power released, just physics
Thats the way a bigger cam or turbo charger adds more power, engine gets MORE AIR so more gasoline can be burned and more energy released, at the 14.7:1 WEIGHT ratio
The 4.0l SOHC engine runs 9.7:1 compression ratio so can not run Regular 87 octane fuel as is
So Ford added a Knock sensor so it can
As air gets warmer the knock sensor has to change spark timing more so power is reduced
You can try 91 octane, or even 89, and see if power comes back during the summer months
Just FYI, Rangers have had Cold Air Intakes since 1986 and the first fuel injected engines
200% air flow thru stock air filter, and at least 150% flow thru air tube from filter box to intake
It pulled air from behind the grill into the bottom of the filter box
I have watched quite a few tests for 3rd party CAIs on several brands of cars and trucks, including Rangers, and they usually either have no effect on power or show less power, never saw any increased power
Car makers sell performance, so if something like a Cold Air Intake helps performance they will added it
Since the 1960s all engines have had performance "headers", scavenging exhaust manifolds, because they added performance
Intake designs with "mini-boost" also since the 1960s
No car maker "detunes" their engines, even for emissions, although the 1970's were an exception, lol
Point is a lot of the "bolt on" parts are sold because they "sound good" and usually won't hurt anything, but if a "bolt on" part was a good idea then the car maker would have already added it