start here.
http://powerstrokearmy.com/forums/showthread.php?t=27648&highlight=boost+leak+detector
do not take the air filter off, and install in its place, unless you have the ccv re-route.
with out the re-route, you install it directly to the rubber pipe that attaches to the turbo itself. the one that reminds you of a funnel.
lower the line pressure of the air compressor, to approximately 25 psi, plug in, and listen. when you find the obvious leaks, then take some soapy water and spray EVERY joint, both sides, top and bottom, and look for bubbles. if all the boots and connections check out, dont forget to check the intake plenum to head. thats also a connection.
if you make a additional adapter, you can install that same thing into the exhaust. there is alot of fking around, as it should be installed directly to the outlet of the turbo. pressurize, and listen.
just because you dont see soot, does NOT mean you dont have a exhaust leak. on a 7.3, especially a stock one thats tuned, even the retarded small leaks can hurt. boost or exhaust.
afterwords, check the icp, and the icp dc, to make sure the hpop is not getting weak. you should be able to maintain 3k psi, at less that 50%. this is, of course, allowing that your current tuning calls for that.
i ran a superchip 1705, on the race tune, towed a GCW of 30k+ of round bales into and out of fields, and up and down the roads, hills and all, and didnt break 1300*. period. if your hot with a superchip, i would bet its a mechanical issue, not a tuning issue.
that said, custom tunes will improve the behavior of that truck DRASTICALLY.
also, if your wastegate actuator is failing, everything else could be checking out as fine, but if your actuator is opening to soon, nothing else will matter, nothing else will fix it.
also, just cuz im curious, what is your fuel pressure set at??
some of these you already covered, but i kinda stopped reading when the bickering started, and skipped ahead, hoping the diagnosing could start fresh, minus the bickering that kinda took over.
so refresh things. what have you tried already, what worked? where are things currently? what have you checked, what have to left to check? what questions do you still need help with?