Actually I have worked on cars with carburetors.
An old style carburetor uses vacuum to inject fuel via a jet (kind of like nitrous) versus an electronic controlled injector.
I am not arguing how a carb works (if it came across like that, then I did not word my statements correctly).
The point I am making is solely about the kit available for our engine.
Here you can see a small carb (very similiar to the weber-alpha ones for the zetec).
Amazing how much it looks like a throttle body.
Now instead of a jet the weber-alpha kit uses fuel injectors at the carb/throttle body.
Very similiar to throttle body injection.
The kit uses a FPR (vacuum) to control fuel delivery (like adjusting the screws on a carb).
The ECU does not controll A/F ratio, simply fuel injector pulse.
The design has many of the positives of both carb & fuel injection and fewer of the drawbacks than each.
The kit brings the zetec to about 180BHP.