loss of power

[tonyearls]

i have a 2000 expedition 4x4 5.4l. I just changed the plugs a few weeks ago and it ran just fine until the other day i tried to go see a friend on the way there i was running just fine until i had to start climbing some hills and then it kicked it self down and i just started to lose speed so i pushed on the pedal and the rpm went above 3000 and i just keep losing speed. then i pulled of and it did not want to ideal unless i gave it gas after a few minutes it started to run just fine so i turned around and went back home and it ran just fine all the way home. when i was sitting on the side of the road you could smell a really strong gas odor. i have drove it around town and it did OK but you try to go with the rpm high there is just no power or try to climb a small grade or hill. any ideal would be appreciated