This is my only complaint with my '04 2500. Between 35-45mph it bogs on lengthy hills. Dodge has now moved to 6speed transmissions to hopefully eliminate this. I have a k&n intake, 4:10 gears, and only use super unleaded when towing. One final thing I do before leaving on a trip (not sure if this works on an '03), I pull the PCM fuse and clear the memory to the transmission. I read this on a Dodge forum. Something in the trans "learns" how you drive and adjusts itself accordingly. Not sure why it does this. But it does work well. Trans will feel much stronger while towing. Eventually it will again "learn" how you drive and will need to be cleared. Just my .02 hopefully it might help.
