Abstract: A method of operating an internal combustion engine is provided which includes the step of determining a desired intake manifold pressure or gas density, based at least in part on a value indicative of a difference between a desired engine speed and an actual engine speed. The method further includes the steps of determining a value indicative of an intake manifold pressure, and adjusting the intake manifold pressure, based at least in part on a difference between the desired intake manifold pressure and the determined value indicative of intake manifold pressure. A software control algorithm for operating an internal combustion engine is provided. The control algorithm includes a first closed loop algorithm for determining a desired intake manifold pressure or gas density, and a second closed loop algorithm for adjusting throttle position, based at least in part on a difference between the desired intake manifold pressure or density and a determined value indicative thereof.