I worked on a guys Explorer a few months ago. His truck would idie fine but lose power at highway speeds. When I checked the codes, it called out egr insufficient flow, iacv and P0305, p0306, and p0300. I checked the freeze frame data and cat temp was 1586*. I told him his cat was clogged. He took it to the dealer and those lazy a55es changed out exactly what the scanner called out. The problem ended up being the cat. Check the freeze frame data on your scanner. also a leaking brake booster will cause a p0171, p0174 callout.