Exhaust gas temperatures (EGTs) are critical to monitor in your diesel. With the high amount of heat that an engine produces, exhaust temperatures can reach nearly 2,000 degrees under a heavy load.
Aluminum (which is used in multiple essential components of a diesel engine, such as pistons, exhaust manifolds, and even the engine heads), has a melting point just over 1,220 degrees. With exhaust gasses capable of reaching temperatures well over the heat capacity of various parts, it is one of the most important things to keep in check. Unfortunately, most vehicles do not come equipped with a way to do this. It is in your best interest to invest in a pyrometer (EGT gauge).
Under heavy load or extreme acceleration, exhaust gasses increase rapidly and can reach temperatures over one thousand degrees in seconds while 1,200-1,300 degrees is nothing to worry about for short periods of time. Extended periods at temperatures over 1,300 degrees are diminishing the life of your engine.
When pulling a heavy trailer up a steep incline, sled pulling or racing EGTs can exceed 1,800 degrees. Anything over 1,500 degrees is doing immediate damage to the engine, such as melting parts of the turbo and internal engine damage; melting, cracking, or even blowing holes in the pistons or any of the other various components, which leads to total engine failure.
High EGTs are caused by excessive fuel or a lack of air; even in stock applications, it is necessary to monitor it with a pyrometer. Doing this can also be beneficial for fuel economy because you can tell if too much fuel is being sent and things are staying in the ideal operating range. If you see your EGTs getting too high the quickest solution is to simply let off the throttle.
All in all, any modification to monitor or decrease EGTs are ideal. Lower exhaust temperatures mean more fuel efficiency and less wear on your engine. Do you have a pyrometer on your engine?