A method for control of output torque developed by an internal combustion engine during the transition from a lean to a rich fueling mode of engine operation, the method comprising: a) with the engine running in a lean fueling mode, processing data values of certain parameters to develop a data value for desired engine fueling for causing the engine to develop a corresponding desired output torque at a given engine speed; b) causing the engine to transit from the lean fueling mode to the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed; characterized by the following steps: processing i) the data value for desired engine fueling resulting from the processing of step a), ii) a data value for engine speed, and iii) a data value for actual air-fuel ratio at which the engine is operating, to thereby develop a data value for desired engine fueling that causes the engine to run in the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed when the engine was running in the lean fueling mode; and wherein step a) comprises: with the engine running in the lean fueling mode, processing data values of engine speed and accelerator pedal position to develop a data value for desired engine fueling for causing the engine to develop a corresponding desired output torque at a given engine speed, and in which step b) comprises: with the engine running in the rich fueling mode, processing a data value for actual air-fuel ratio through a function that correlates data values of air-fuel ratio to data values of engine fueling for causing the engine to run in the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed when the engine was running in the lean fueling mode, and causing the data value of desired engine fueling to be the data value of engine fueling correlated by the function to the data value of actual air-fuel ratio. a) with the engine running in a lean fueling mode, processing data values of certain parameters to develop a data value for desired engine fueling for causing the engine to develop a corresponding desired output torque at a given engine speed; b) causing the engine to transit from the lean fueling mode to the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed; processing i) the data value for desired engine fueling resulting from the processing of step a), ii) a data value for engine speed, and iii) a data value for actual air-fuel ratio at which the engine is operating, to thereby develop a data value for desired engine fueling that causes the engine to run in the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed when the engine was running in the lean fueling mode; and i) the data value for desired engine fueling resulting from the processing of step a), ii) a data value for engine speed, and iii) a data value for actual air-fuel ratio at which the engine is operating, to thereby develop a data value for desired engine fueling that causes the engine to run in the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed when the engine was running in the lean fueling mode; and wherein step a) comprises: with the engine running in the lean fueling mode, processing data values of engine speed and accelerator pedal position to develop a data value for desired engine fueling for causing the engine to develop a corresponding desired output torque at a given engine speed, and with the engine running in the lean fueling mode, processing data values of engine speed and accelerator pedal position to develop a data value for desired engine fueling for causing the engine to develop a corresponding desired output torque at a given engine speed, and in which step b) comprises: with the engine running in the rich fueling mode, processing a data value for actual air-fuel ratio through a function that correlates data values of air-fuel ratio to data values of engine fueling for causing the engine to run in the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed when the engine was running in the lean fueling mode, and causing the data value of desired engine fueling to be the data value of engine fueling correlated by the function to the data value of actual air-fuel ratio. with the engine running in the rich fueling mode, processing a data value for actual air-fuel ratio through a function that correlates data values of air-fuel ratio to data values of engine fueling for causing the engine to run in the rich fueling mode while maintaining engine output torque at the corresponding desired output torque at the given engine speed when the engine was running in the lean fueling mode, and causing the data value of desired engine fueling to be the data value of engine fueling correlated by the function to the data value of actual air-fuel ratio.