2001 Dakota Power

I have an 01 Dodge Dakota 3.9 2X4 with 104,000 miles. When I am driving slow or in town it runs fine. When i am on the highway going a little faster it suddenly looses power when i have the pedal held steady in one spot. It will gradually slow down unless i put it to the floor, then it will down shift and run great for a few minutes. It happens a few times a day. I doesnt idle at all and i know it needs an IAC. Would that have anything to do with it. Any ideas? Thanks.

could be lots of things fuel pressure plugged exhaust get it scanned for DTC's and report back

There are no codes. Checked the TPS, and IAC and they are ok.