Computer hardware relating to the land and water vehicle industry; computer that interfaces with and communicates information on a data link for engine and/or transmission tuning, testing, and performance management, and electronic automotive diagnostic equipment; tuners, namely, electronic motor vehicle ignition, power train, and transmission tuners; calibration instruments, namely, computer hardware for engine and transmission calibration; fault diagnostic equipment for use in servicing of land and water vehicles, namely, electronic vehicle diagnostic computer hardware for use in interfacing with a vehicle's onboard computers; apparatus for performing diagnostic analysis of electronic components, namely, computer and computer systems comprising computer hardware and firmware for retrieving and clearing diagnostic trouble codes for computerized systems in vehicles; diagnostic apparatus for use in land and water vehicles, repair and maintenance, namely, an engine diagnostic computer connector for identifying faults in the combustion system and computerized system in vehicles; electronic cables; measuring, signaling apparatus and instruments, namely, digitizers, gauges, namely, air/fuel ratio gauges, boost gauges, vacuum gauges, temperature gauges, namely, intake and exhaust gas temperature gauges, voltage gauges; the foregoing signaling apparatus and instruments also being output to or readable via screen, monitor or computer display; apparatus for recording, transmission or reproduction of data