Are EFI diesels de-tuned from factory?

Q. Is it true that EFI diesels like my Mazda BT50 are deliberately de-tuned from the factory? Don’t get me wrong, the truck’s a rocketship compared to my old petrol Bravo and I’m loving it to death, but I read about the engines being deliberately chocked via the ECU, and that there’s free power to be had. Is this generally true or just another one of those campfire tails? What can be done in particular to my ute to get it going even harder? 

A. Every engine has a limit and manufacturers usually leave lots of spare safety in an engine just in case some guy never changes his engine oil or air or fuel filters. So if he is really lazy then he can get away with slack maintenance and probably won’t have the engine cough and splutter for long after it’s due for service. Tune the engine up for example with a chip (which you will need to have to tune an EFI controlled BT-50) and you start to eat into that ‘spare tune area’. So yep you certainly can chip up a common rail engine like yours and just remember to always keep it ‘serviced by the book’. With a chip that offers fuel and timing control and isn’t over-tuned (overpowered) you should see a very long life out of your Mazda.