Took a little trip this week and when I gave my Expy some gas to pass, the RPM's would run up like it had dropped into 3rd but would slow like I had a tranny slipping. With the cruise on the engine would jump from 2 grand to 3 on an incline but would actually slow speed wise. I'd have to disengage the cruise and just hold steady pedal to keep it at an agreeable speed and slowly get it up to the speed limit again . Getting on an on-ramp was like pedaling a bike in a head wind. Just had to take about twice the normal distance to get up to 70 since it would not accelerate at all at WOT and was very sluggish at 3/4. Moderate acceleration in town traffic it would do fine. Drops into lower gear and moves along OK...but when going past 3/4 it peters off. Also have two codes...PO171 and PO174. Not sure if these are related to the problem.