The issue with 6.0's losing head gaskets comes from the EGR getting clogged and then overheating. It can heat to over 2500 deg F when the EGR gets clogged.
I disagree, if the EGR was to plug up then if anything you would have a cooler running engine. That is the whole basis of a EGR delete kit, plug of the EGR and eliminate the cooler, lower you EGT's and increase top end hp. With a clogged EGR you will get a EGR flow insuffiecient engine code/check engine light. A leaking EGR cooler is a different story.
There are many causes of headgasket failure on 6.0's, a carboned up EGR is not one of them. (if the EGR valve it self gets carboned up it will often cause smoke and a poor running engine along with a lack of power complaint.) Unlike the 6.6 duramax the 6.0 has no turbo vane position sensor, the engine calculates vane position based on boost pressure, exhaust backpressure, engine load, speed, throttle postion and many other things. If you have a small boost leak the engine will try to compensate and ramp the vanes closed to make the boost. By the time it see's that something is wrong between the corelation (sp?) of all the sensor's it monitors it would have subjected that engine to very high exhaust backpressure, upwards of 80psi. That will take out your headgaskets and egr cooler, that is one of the main reasons for headgasket and egr cooler failure. Chips and anything that boosts hp/boost will have an effect on this, Ever wonder why some ford diesels seem to have an exhaust whistle when just idleing or off idle, the chip/tuner will close the turbo vanes to make the boost faster, thereby causeing the engine to have more exhaust backpressure.
Note: There are also a few years of 6.0 fords, 03-05 or so that do not use a exhaust backpressure sensor (the initial 03-04 did but the sensor was later ignored with a reflash), these trucks have much more issues then the ones that use an exhaust backpressure sensor as the pressure is an infered reading.
To hit 2500F on a pyro is insane, you would have to be running more fuel through there then any diesel truck I have ever heard of (plus a 6.0 cant fuel as hard as the other trucks, they are limited by the HEUI system). Any sustained run over 1250F you are asking for trouble, hell I can only spike mine to 1700 or so and I have a lot of fuel going in there.
Simply put the 03-04.25 6.0's are turds, the second generation got better and by late 05, early 06 they had the vast majority of bugs worked out, but they still have issues.