Programming a reference voltage in a reference cell of a charge-based memory to a level that will maximize the predicted operational life of the memory, based on the application-specific predicted usage profile of the memory and the effects of that usage profile on the leakage curves of the various memory states. A filter is provided in the cavity and the cylindrical body is mounted for rotation in a housing through which the exhaust gas flows. An event system receives the events and determines whether an alarm condition exists. The other, normally smaller vapor injection ports are open for both vapor injection and by-pass unloading operation.