Now Goonarmy and The Mad Hat Man, behave yourselves!
NOx in a diesel! Nitrous Oxide NO2 .... laughing gas ..... anaesthetic gas .....
Goony is right though. Until the black smoke point all diesels are running with excess oxygen in the cylinders, so throwing in NO2 won't do any good except to make nitric and nitrous acids in the exhaust which is probably not top of the good ideas list, UNLESS you can also heave in extra diesel ONLY when the NO2 is going in. Anyway, You would need to be carrying gigantic gas cylinders to have enough NO2 to have any effect for more than a few seconds.
It is entirely different from petrol engines in which the air-fuel ratio matters, and where the amount of oxygen (air) getting into the cylinders is the limiting factor. In the turbo diesel the sky's the limit power-wise if you care to hoick up the turbo to 7 BAR / 100psi .... Sometimes too many horse-power happens ...
CharlesY