the 3rd gens will run much higher egts than the earlier 12 and 24v's. 1300* preturbo(1000post) is normal for them under wot.
there are 3 primary ways to lower egt.
#1 take your foot out of it.
#2 turbo upgrade
#3 h20/meth

 

To comment on #'s 2&3 of your post, what about simple bolt ons, a TRUE cold air intake system, exhaust, and a boost fooler? Would a boost fooler do anything for EGT's on a STOCK (no electronics) truck???

 

a boost fooler will give you a few more psi, which will help your egt's a slight bit. nothing will be better than replacing the stock turbo with a unit designed for towing. the factory turbo is a compromise. it must build boost quick and support the 325hp that the factory has rated the truck at.
a turbo is not cheap. water is cheaper, but is really masking an issue. something must be done to improve the volume of air. spinnng the factory turbo faster will do this(boost fooler) but after about 35psi, gets out of its efficiency range and will start to increase egt's.

i have upgraded the turbo, and have no gotten to the point of needing more air, or masking the issue at hand.

 

Not all 3rd gens were manufactured to run higher EGT's.

Not which years but I do know the 03 and 04 trucks have problems with valve seats coming loose if too much heat is put to them.

The 06 and early 07 5.9 trucks can run much higher EGT's due to better valve seats.

Now take what I say with a grain of salt as I'am only repeating what I have read and learned from others.

Not sure about the 04.5 and 05 trucks.

 

i didnt mean capable of running sustained high temps. i meant the egt's were designed high from factory to keep the cat lit off, hence the 3rd injection event. and i meant 04.5 and up. sorry