[ElKotze]

You are correct, Bigdav, some systems do use a Manifold Absolute Pressure (MAP) sensor, while others use a Mass Air Flow (MAF) sensor. While a MAF sensor meters the amount of air going into the engine, a MAP is basically just a pressure meter. MAF sensors systems are
more accurate. A MAP sensor can not read density, which changes with temperature, so an additional temp sensor is necessary. EFI systems using MAF make tuning adjustments in open loop operation based on the input it receives and at WOT goes into closed loop operation. MAP systems on the other hand determine it's air/fuel-ratio and ignition curves on preconceived maps. Rather than tuning in open loop it takes it's sensor signals and select a pre-programmed map. That's also the reason why MAP systems cannot compensate for a power-adder, like a blower, while MAF systems can compensate even for aggressive power-adders.
The wide-band O2 meters the amount of O2 in the exhaust gas which helps to adjust A/F-ratio.