Heh now you are gonna want to get the FU chip cuz you will be addicted to the 100hp and not want to go lower.. esp if you are getting that kind of MPG... when u pick a tow tune, basically you just need to watch your EGT and Trans Temps. go with the best tune that doesn't put those in the danger zone. Keep in mind the Outside air temp will affect the actual tranny temps...
time to add the 120 or 140 HP tune heh