E250 lacking power

[MontanaBighorn]

hello,
i drive a '00 ford E250 4x4 service van and im finding that (due to a combination of the 3000# load im hauling, the high gear ratio, and the 265/75 r16 tires) the 5.4 liter engine just doesnt make enough power to maintain highway speed (65-75 mph). the van continually downshifts into drive and is constantly locking/unlocking the torque converter trying to maintain speed. ive had the van checked out and tuned up (by the dealer) with no difference at all. im currently getting about 8.5 mpg.

i purchased an edge CTS (#85250) that is compatibile with the F150/F250/F350/excursion/expedition with the 5.4 in hopes that it would create the necessary power to at least be able to maintain 70 mph on the highway. to my disappointment, the CTS does nothing. it will monitor stats and list/clear error codes but it will not adjust power levels.

after contacting edge several times (only to be told "sorry, e250 is not supported") one of the techs referred me to this site.

if there is anything you guys can do to make my CTS compatible with my E250 it would be greatly appreciated.

thanks!