One year, the new tractors that entered service in our fleet came with the engine rated at 350. and I bribed one of the guys in the shop to reprogram the 'puter in my assigned tractor. Then another driver did it. And then another. Fleet manager pulled in these tractors for an inspection because their acceptable mpg' s were below the acceptable norm. They were sent to Cummins. Cummins found who did what when by checking the time stamp in the data logger. Well, that ended that and they punished the drivers by limiting the top speed to 62 mph until their mpg average fell back into the normal range. That sucked.