First off, I have been through all this.... The reason the truck over heats is beacause its low on antifreeze, from it loosing too much out of the overflow. This is called "puking" and is somewhat of a "normal" thing to happen if a break down would be a normal thing. The reason it does it at high boost is beacause the poor design of only 3 head bolts per cylinder. It does not have enough strength to hold the heads down. The bolts start to stretch at high boost aplications and parts of the head gasket start to fly out. (is you truck stock, or does it have a reason to run higher boost then stock like tuned up) When the truck over heats the heads like to start warping and cracking. The 05' trucks got a new head gasket design because of the many problems with the 03, and 04 models. The new design helped alot but is still not a total fix. My truck is an 04' that began "puking" and over heating 2 weeks after i tuned it, with 12,000 miles. After blowing up a couple radiators i convinced ford i had blown gaskets, so now i have the 05' gaskets, they lasted for 3 months, and now i em' havin some problems, but not as bad as the old gaskets. (i drive my truck HARD!) I would be very mad at you dealer for not having you a truck to drive. I know my dealer lost my business and our family and farms over the fact I couldn't get a rental because i wasn't 21?! when my truck was in for 3 weeks. Oh yeah, ask them what is taking so long, because if the parts are sitting there the ford manual says it takes only 20 hours of work to put new head gaskets on a 6.0. Some people are starting to try using a high grade head stud to fix the problem. One of my friends just got some installed on his truck after having these problems. I'm waitng to see how it works for him, and might end up going that way. studs cost around 800, and 1800 to install, b/c you have to pull the engine.
04' F-250 FX4 XLT Sport, 6.0L PSD, Torqshift, Crewcab, Spray-in bed liner, 6-Gun w/ Speedloader over Super Chips, Magnaflow stainless steel single exhaust (muffler delete), K&N FIPK intake, remote start.
95' F-350, 7.3L PSD, 4X4 off road, standard cab, 5" stacks, 36" Trxus, 6" lift, 3.73's, ladder bars, nerf bars, pyro and boost gauges, Banks chip, Banks intercooler, downpipe, K & N Intake, Schied injectors, dual disk McLeod, Pain.