While yes I agree diesel engines loose much torque at the top end, the reason that it falls off on a STOCK engine is becuase the IP is shutting down the fuel. If you turn up the max speed (aka the max idle speed adjustment...its confusing...don't ask) then the IP won't cut the fuel off and thus you won't see that same huge torque dropoff at redline.

Those who are more diesel engine savvy know that the "Full Load" adjustment is also known as a "torque capsule" adjustment on other types of injection pumps. This must be kept in mind that when you increase the fuel across the range...

Its difficult to explain...easier to understand after an IP is all torn apart on your bench