Originally Posted by username taken

Get your hottest readings with a stock program and use those as a baseline "limit." I don't think the aftermarket gauges are very accurate, due to variations in probe placement, depth, etc. People with stock engines are reporting wildly varying readings under similar conditions, leading me to believe that the gauge is not an absolute, but rather a relative reference point. If the hottest you ever saw stock is 1100, I wouldn't push it past that after mods. Similarly, if your truck is maxing out at 1450 stock, I would feel safe going that high even after mods.

I got the following response from an inquiry directly to Cummins:
Regarding your inquiry about Safe EGTs.

Thanks for your Email message. You have contacted Cummins, Inc. at our
Customer Assistance Center located in Columbus, Indiana. This is our
worldwide headquarters and has been our home since Clessie Cummins founded
the company February 3, 1919.

Cummins engines, working near the limit of their capability, can produce
exhaust gas temperatures in the range of about 1300 degrees F when measured
before the turbocharger. We do not give out maximum (DO NOT EXCEED)
exhaust temperatures because pyrometers, especially the type that are sold
for automotive use, are often inaccurate and have a time lag between when a
temperature is generated and when it is displayed.

Aftermarket uprate hardware can change fueling, timing and boost. These
products can produce huge changes in exhaust temperatures.

Engines that have not been altered from their as-manufactured state will
not produce dangerously high exhaust temperatures. We would not know
exhaust temperature might be dangerous for engines that have been modified.

In a nutshell - a stock engine will not melt down, and similar EGT's after bombing shouldn't either.