A method and control apparatus for an internal combustion engine that allows an operator to calibrate engine performance relative to an engine operating characteristic. The control apparatus comprises a base engine control map that correlates values of the characteristic with values of a base engine control, a trim control map that correlates the values of the characteristic with values of a trim control, an engine control unit that obtains from the base engine control and trim control maps the respective base engine control and trim control values that are based on the characteristic value, and a panel that is operatively coupled with the engine control unit and includes a first switch regulating a trim signal supplied to the engine control unit. The trim control map is separated from the base control map. The engine control unit calculates an engine operating control value based on the obtained values. The calculated engine operating control value is supplied to the internal combustion engine to vary the engine performance. The first switch is adapted to be manipulated by the operator. And the trim signal causes the engine control unit to modify the trim control values in the trim control map.