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The EEC does know how much fuel should be being injected as it monitors the O2 sensors in closed loop operation. It will adjust injector pulse widths if needed to richen or lean depending on whether there is too much or too little fuel. In open loop (wide open throttle - WOT) the EEC ignores the O2 sensors and goes straight to the table look ups for fuel and spark. So, you can tune your fuel needs at WOT with the fuel pressure regulator and the EEC will tune A/F ratios back into spec when running part throttle normal driving conditions. This keeps fuel consumption at or close to stock.