My 5.0 seems to run good, idles perfect, but when i drive it i cannot accelerate in drive or overdrive unless i am downhill or the wind is behind me. I have a top speed of 55mph (on the speedo, actual speed more, i have 35's on it). I also have a built trans with a 2000 stall. Needless to say, i rarely hit overdrive speeds. When i press down the pedal to accelerate it acts like the throttle cable is unhooked, no change in rpms or anything untill it shifts down a gear and revs high. Any suggestions?

 

Pull the codes to see if anything has been flagged.
Has any engine work been done - tune-up, etc.?

 

Simply not making enough power.. 5.0's have to rev to make power