Yes exactly, "fuel follows air" (have worked on ECU firmware, and current ride is a 2003 with a wire between the pedal and throttle). As you said, a sensor (and computer) measures air -- volume, temperature, etc. -- estimates oxygen content, and (of course there are many other factors) then calculates how much fuel to squirt in.

I used to race cars, and I still have the old 2003 5-speed turbo, but the idea of an electric car without all the hoses and fluids and spinning pieces is attractive.