carbs just cant give you spot on fueling everywhere and std ecus are set by car makers and have to create somthing thats is designed to make an engine econimcal,quiet,smooth,enviromental and long lasting you can do some basic ajustment if you can get in, but are hardware limited.
any programable ecu is the door to running what ever you want or need plus everythin is ajustable to what you want
at college we had a std n/a toyota twincam on a bench dyno with 4 gas ( widebands where very rare at the time) and loads of other monitor equipment with two ecu setups one std toyota ecu and hardware and the other was a early programable unit that was swaped over from the std toyota one all other hardware was unchanged
the toyota ecu was programed by toyota and would retard ign in areas to reduce noise and run lean in other areas for enviromental regs etc
when the programable unit was used set to optimum fueling and timing the torque plot was way higher at all rpms and had no holow points just one big nice arc.
we used this bench dyno for all sorts of sudies on engine manigment and automotive eletronics
i did not cover actual live dyno mapping just the effects of modern engine magement, live mapping was done by the motorsport enginering students but we did share lots of the same classes together in my 3rd year
corse if anyone here actualy has anymore experince here than me im all ears
also done some work with diesel engines on a realy old water brake dyno if anyone here knows them