Actually i'm in Nevada right now, and I don't have an F150 at this time. but I have a 36 ft RV with a Ford V-10 1999 Mountainaire. I was driving up Donner pass on my way to Reno, it goes up over 7400 ft elevation. On the steep parts where the engine would get up over 4000 rpm it started missing and got increasingly worse the higher I got. Is that just the nature of these things?= high elevation and maybe cheap gas? Thanks for your help. I'm down in lower elevation now but haven't really run it uphill again. I'll let you know what happens