Howard, where are you located?
It's a long shot, but I'm hoping you'd be close to north carolina.
As far as I know, although the 2002-2003 7.3Ls may have it, there is no wastegate on your turbo. You should be hearing whistle from your turbo. gentle throttle, you should hear a whoooooooOOOOOO increasing with engine rpm, moderate throttle, to heavy throttle, it should sound very similar to a big rig(although not as loud as a screaming caterpillar, lol) with the high pitched whistle. Take the cowl off the mototr(i'm sure it's already off)
take the intake hose off of the turbo, and grab the impeller, and spin it, it should spin for several seconds. Then, grab the impeller, and move it in and out, should have barely perceptible play, and no up and down movement at all. Also, inspect the condition of the fins.
How does the engine itself idle, run, does the van shake at all? Is it smooth?
Whoops gotta go, more later!