A system that measures the density of the air in the intake of an internal combustion engine and calculates the gain or loss in performance provides a display to an operator in real time in a single, quickly assimilated reading. A display can indicate the combined power increasing effects of turbo/superchargers that increase density and power by compressing the air, as well as charge air coolers that increase density by decreasing the temperature. Density can be measured directly, or calculated from sensor readings. Densities, as well as temperatures and pressures can be displayed as absolute values, as percentage gains or losses verses a known reference such as ambient, or as a loss or gain between density increasing devices to indicate the individual performance of the component. One embodiment incorporates a cradle mounted PDA type handheld computing device on the dashboard to provide the display, input/output and processing hardware.