We have spent a lot of time with the 7.3 platform and have found great ways to get more HP and fuel Economy as well as reliability. One of the ways we are able to make such great tunes is because we use a load Dyno to make all of our tunes. Then we work on drive-ability and shifting so we can get the power to the ground with a smooth crisp feel.
Something else that will make our tunes stand out over the can TS tunes is the shifting strategy. Since your truck is a 03 that means that you have a VDH PCM and with our tunes we will swap you over to an improved shifting strategy.
I hope this help and if you have any more questions like HP #'s, TQ #'s, Mileage, EX we will be happy to help.