The 7.3 in your 2001 is a different beast to what most are talking about here, not sure what to suggest. But the warnings are for the 6.0, the 7.3's seem to take HP increase very well.
FYI, I have an SCT tuner with stock SCT tune on the 6.0 since it's the only tuner that you can delete the EGR warning light with, I picked up 3~4mpg with it, no extra heat in the water/oil/trans temps or EGT. But I do think the MPG I picked up is mainly due to the better trans shifting and TC lockup, which is something you can't change on the 7.3 with a tuner.
While I believe SCT it the best options for a 6.0 from everything I have read, I don't think that's true of the 7.3. You may want to ask in the forum below since many have 7.3's in vans, and some very highly modified. http://www.thedieselstop.com/forums/f14/