[aerohead]

1) The concept is valid. In the early 1990s, GM brought an Oldsmobile to Bonneville, where they made run after run with different chips. The attache they were carried in was referred to as the 'million-dollar briefcase.'
2) Variable-Valve-Timing might still be a function of oil pressure, but ignition timing, fuel injector nozzle dwell , and turbo waste-gate would remain candidates for electronic controlled.
3) For EPA compliance and vehicle certification, one might presume that the automaker had already optimized the ECU and sensors.
4) Personally, I'd avoid them like how people used to avoid plagues.
5) For meaningful fuel savings, one has to attack rolling resistance and aerodynamic drag.
6) You can purchase a bona-fide 350%-to-400% mpg improvement today simply by moving to an electric vehicle.