HFM-SFI was a big leap foward into full electronic computerized engine management .
The A/F mix, ignition timings, and idle/rpm are all ECU controlled electronically
with all sensor inputs to ECU . It can be chipped , but not really needed , as parameters and mapping are amazing.
They have good diagnostic storage cababilities and live steam data .
Injectors are electronic and duration times are ECU controlled , as is ignition for each cylinder to provide optimum performance.Ignition is direct coil over waste spark system . Variable valve timings and variable intake runner length
also are ECU controlled and add to the performance .
Quite a system for that time frame..
Google EFI HFM and yuo can find lots of tutorial info