Some E38 OS's have a "stomp fuel" PID available that pulls the info directly from the ECM. Unfortunately, it only works with laptop logging ( I think ) and it's not available for my OS, so I can't test it anyway. Transient can make a huge difference to the way the car drives and in reality, I don't think a calc-pid is going to do the job. You really want to know what the ECM is actually using, as we don't have the full calculation that GM is using. For example, transient fuel is going to change with differences in MAP, TPS, RPM and possibly even charge temp. This is true for both throttle open and throttle close and there is also residual fuel in the manifold even when the engine is in a stable condition.
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